Compressed sensing applications for biological microscopy Marim, M., M. Atlan, E. D. Angelini, and J.C. OlivoMarin IEEE Workshop on Signal Processing Systems, SiPS: Design and Implementation, 216221 (2010)
Résumé: This paper provides an overview of some compressed sensing contributions to biological microscopy developed in our laboratory. They are mainly on four topics: (i) a CSbased denoising framework exploiting a Total Variation sparsity prior and very limited number of measurements in the Fourier domain, (ii) practical experiments on fluorescence image data demonstrating that thanks to CS the signaltonoise ratio can be improved while still reducing the photobleaching effect, (iii) a CS reconstruction framework combining Fourier magnitude measurements and Fourier phase estimation for sequential microscopy image acquisition, (iv) a microscopy acquisition scheme successfully combining Compressed Sensing (CS) and digital holography. ©2010 IEEE.
Motsclés: Compressed sensing; Denoising; Digital holography; Fluorescence microscopy; Photobleaching; Biological microscopy; Compressed sensing; Denoising; Digital holography; Fluorescence image; Fourier; Fourier domains; Magnitude measurement; Phase estimation; Photobleaching effect; Total variation; Computer generated holography; Fluorescence; Fluorescence microscopy; Fourier transforms; Noise pollution control; Photobleaching; Signal processing; Signal to noise ratio; Signal reconstruction


Optimal subsampling of multichannel damped sinusoids Chardon, G., and L. Daudet 2010 IEEE Sensor Array and Multichannel Signal Processing Workshop, SAM 2010, 2528 (2010)
Résumé: In this paper, we investigate the optimal ways to sample multichannel impulse responses, composed of a small number of exponentially damped sinusoids, under the constraint that the total number of samples is fixed  for instance with limited storage / computational power. We compute CramérRao bounds for multichannel estimation of the parameters of a damped sinusoid. These bounds provide the length during which the signals should be measured to get the best results, roughly at 2 times the typical decay time of the sinusoid. Due to bandwidth constraints, the signals are best sampled irregularly, and variants of Matching Pursuit and MUSIC adapted to the irregular sampling and multichannel data are compared to the CramérRao bounds. In practical situation, this method leads to savings in terms of memory, data throughput and computational complexity. © 2010 IEEE.
Motsclés: Array signal processing; Compressed sensing; Spectral analysis; Array signal processing; Bandwidth constraint; Compressed sensing; Computational power; Damped sinusoids; Data throughput; Decay time; Exponentially damped sinusoids; Irregular sampling; Limited storage; Matching pursuit; Multichannel; Multichannel data; Multichannel estimation; Number of samples; Spectral analysis; Optimization; Sensor arrays; Signal processing; Signal reconstruction; Spectrum analysis; Computational complexity


Image transmission through an opaque material Popoff, S., G. Lerosey, M. Fink, A. C. Boccara, and S. Gigan Nature Communications 1, no. 6 (2010)
Résumé: Optical imaging relies on the ability to illuminate an object, collect and analyse the light it scatters or transmits. Propagation through complex media such as biological tissues was so far believed to degrade the attainable depth, as well as the resolution for imaging, because of multiple scattering. This is why such media are usually considered opaque. Recently, we demonstrated that it is possible to measure the complex mesoscopic optical transmission channels that allow light to traverse through such an opaque medium. Here, we show that we can optimally exploit those channels to coherently transmit and recover an arbitrary image with a high fidelity, independently of the complexity of the propagation. © 2010 Macmillan Publishers Limited. All rights reserved.
Motsclés: article; imaging system; laser diffraction; light scattering; optical tomography; visual system


Thermomechanical properties of Yb3+ doped laser crystals: Experiments and modeling Petit, J., B. Viana, P. Goldner, J.P. Roger, and D. Fournier Journal of Applied Physics 108, no. 12 (2010)
Résumé: Thermal conductivity values of several laser materials were determined by photothermal measurements and compared to predicted values. The effect of the ytterbium doping concentration could be modeled using a simple cationic mass difference model. For ytterbium content corresponding to an absorption coefficient of 10 cm1 (or 85% absorption of the pump power) Yb: GdVO4 (caxis) and Yb: Gd3 Ga5O12 laser materials present the highest measured thermal conductivity values of 8.1 W m1 K1 and 7.7 W m1 K1, respectively. Yb: Y3 Al5O12, Yb: Lu 3Al5O12, Yb: CaGdAlO4, and Yb: YAlO3 belong to the 67 W m1 K1 range while Yb: CaF2 and Yb: Lu2 SiO5 are situated in the 56 W m1 K1 range. Other matrices such as Yb: SrLaGa3O7, Yb: CaGdAl3O7, Yb: SrGdGa3O7, and Yb: BaLaGa3O7 have thermal conductivity values lower than 5 W m1 K1. With the knowledge of the thermal conductivities and the determination of the thermal expansion coefficients, thermal shock parameters are evaluated for several ytterbium doped laser hosts. © 2010 American Institute of Physics.
Motsclés: Absorption coefficients; Belong to; Laser crystals; Laser materials; Mass difference; Photothermal measurements; Pump power; Shock parameters; Thermal expansion coefficients; Thermomechanical properties; Ytterbium doping; Ytterbiumdoped laser; Absorption; Doping (additives); Gadolinium; Gallium; Pumps; Silicon compounds; Thermal conductivity; Thermal expansion; Ytterbium


Numerical prediction of frequency dependent 3D maps of mechanical index thresholds in ultrasonic brain therapy Pinton, G. F., J.F. Aubry, M. Fink, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 22582261 (2010)
Résumé: Therapeutic ultrasound has been used in brain therapy for thrombolysis and thermal ablation. Two approaches are used to transmit acoustic energy through the skull to the brain: low frequency ultrasound, with a wavelength that is larger than the skull thickness, and high frequency ultrasound, that is sensitive to aberrations and must use corrective techniques. At high frequency the Mechanical Index (MI) is lower, which translates to a higher cavitation threshold. The goal of this study is to determine if there is a comparable acoustic environment during high intensity focused ultrasound (HIFU) brain ablation at a high frequency by evaluating the volume that is above various MI thresholds for different device geometries that correspond to each treatment. The acoustic field was modeled with a 3D finite difference fullwave acoustic code developed by the authors that has been previously validated in a general acoustic context and with registered skull experiments. In addition to the non focused geometry of a 300 kHz blood clot treatment device two types of focused therapeutic transducers were modeled: a low frequency 300 kHz transducer, and a 1 MHz transducer that required aberration correction with a time reversal approach. It is shown that the brain volume above a range of MI is over three orders of magnitude larger at 300 kHz compared to 1 MHz. © 2010 IEEE.
Motsclés: Aberration correction; Acoustic energy; Acoustic environment; Blood clots; Brain therapy; Brain volume; Cavitation thresholds; Device geometries; Finite difference; High frequency; High frequency ultrasounds; High intensity focused ultrasound; Low frequency; Lowfrequency ultrasound; Mechanical indexes; Mechanical indices; Numerical predictions; Therapeutic ultrasound; Thermal ablation; Three orders of magnitude; Thrombolysis; Time reversal; Ablation; Acoustic fields; Transducers; Ultrasonic tes


Detection and imaging of human beings behind a wall using the dort method Davy, M., T. Lepetit, J. De Rosny, C. Prada, and M. Fink Progress in Electromagnetics Research 110, 353369 (2010)
Résumé: In recent years, through the wall imaging has become a topic of intense research due to its promising applications in police, fire and rescue or emergency relief operations. In this paper, we propose to use the DORT method (French acronym for Decomposition of the Time Reversal Operator) to detect and localize a moving target behind a wall. One of the DORT method major strengths is that detection remains possible through a distorting medium. In this paper, the DORT method is successfully applied to detect and track moving human beings behind a thick concrete wall. The smallest detectable displacement is also investigated.
Motsclés: Concrete wall; Decomposition of the time reversal operator; Emergency relief; Human being; Moving targets; Through the wall imaging; Law enforcement; Walls (structural partitions)


Noninvasive assessment of myocardial anisotropy in vitro and in vivo using Supersonic Shear Wave Imaging Lee, W.N., M. Couade, C. Flanagan, M. Fink, M. Pernot, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 690693 (2010)
Résumé: The knowledge of the myocardial fiber architecture is deemed essential and yet to be nondestructively investigated for myocardial mechanics and its association with the progression of myocardial diseases. In this study, Supersonic Shear Wave Imaging (SSI) was performed for its first time to noninvasively assess the fiber orientation (i.e., anisotropy) in in vitro porcine (N=5) and in vivo openchest ovine (N=1) hearts. The SSI technique combined with the coherent planewave compounding method was performed to achieve both high echocardiographic image quality and ultrafast frame rate (8000 fps). An 8 MHz linear array probe (pitch =0.2 mm) was mounted on a customized rotation device, which allowed 360 rotation at 5° increments. The probe was initially aligned (±90° inclination) with the longitudinal axis in the local cardiac coordinates. The variation of the myocardial fiber orientation across the wall was observed in both in vitro and in vivo cases. Myocardial fibers were oriented gradually from the left diagonal (upper left to bottom right) near the epicardium (100% wall thickness) to the right diagonal (upper right to bottom left) near the endocardium with the midwall region dominated by the circumferential fibers. This finding was in good agreement with the literature and histology and has demonstrated the feasibility of SSI in mapping myocardial anisotropy. © 2010 IEEE.
Motsclés: anisotropy; fiber; myocardium; shear wave; supersonic; ultrafast; Echocardiographic images; Frame rate; Invitro; Invivo; Linear arrays; Longitudinal axis; Myocardial disease; Myocardial fiber architecture; myocardium; Noninvasive assessments; Plane wave; Shear wave imaging; supersonic; Ultrafast; Wall thickness; Anisotropy; Echocardiography; Elasticity; Fibers; Heart; Image quality; Probes; Rotation; Shear waves; Ultrasonics; Shear flow


Aberration correction using moving particles speckle noise for ultrafastultrasonic imaging Osmanski, B.F., G. Montaldo, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 983986 (2010)
Résumé: The correction of sound speed heterogeneities is an important problem intransskull and deep organs imaging. Among all the proposed adaptive focusingmethods, time reversal is an elegant one that enables to know the Green'sfunction between the ultrasonic array and a punctual scatterer. However, in theabsence of strong well resolved scatterers, time reversal is not useful. In thiswork we propose to use the echoes coming from moving particles in a flow togenerate a virtual pointlike scatterer and focus on it by iterative timereversal. This method enables to focus adaptively anywhere a flow is present.Then we use the Green's function to correct the ultrasound images. First, weapply this technique using focused wave then to improve it, we use the ultrafastplane wave imaging and synthetic focusing © 2010 IEEE.
Motsclés: aberration correction; flow imaging; focusing; time reversal; ultrafast imaging; Aberration correction; Flow imaging; Focused waves; Moving particles; Sfunction; Sound speed; Speckle noise; time reversal; Ultrafast imaging; Ultrasonic arrays; Ultrasound images; Wave imaging; Green's function; Scattering; Ultrasonic applications; Ultrasonics


Adaptive focusing of transcranial therapeutic ultrasound using MR AcousticRadiation Force Imaging in a clinical environment Marsac, L., B. Larrat, M. Pernot, B. Robert, M. Fink, J.F. Aubry, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 991994 (2010)
Résumé: Background: In order to focus ultrasound beams through aberrating layerssuch as fat or bones, adaptive focusing techniques have been proposed to improvethe focusing, mostly based on the backscattered echoes. We recently proposed anenergybased technique with the sole requirement being knowledge of theacoustic intensity at the desired focus. Here, Magnetic Resonance AcousticRadiation Force Imaging (MRARFI) is used to map the displacement induced by theradiation force of a focused ultrasound beam. As the maximum displacement isobtained with the best corrected beam, such a measurement can lead to aberrationcorrection. Material and methods: Proof of concept experiments were previouslyshown in a small animal MR at 7 T using a 64elements linear phased arrayoperating at 6 MHz. Optimal refocusing was then obtained through numerical andphysical aberrating layers. This work is extended here in a clinical Philips 1.5T Achieva scanner. The HIFU beam is generated using a 512 elements US phasedarray (SuperSonic Imagine, France) dedicated to transcranial human experimentsand operating at 1 MHz. Experiments are conducted in phantom gels and ex vivobrain tissues through numerical phase aberrators. A motionsensitized spin echosequence (TE 70 ms, TR 1200 ms, spatial resolution is 227 mm 3) isimplemented to measure displacements induced by the acoustic radiation force oftransmitted beams. Results: MRARFI allowed mapping the distribution of theradiation force at the focus of the array. After the recording of the MR phasesignals for different US emissions, the proposed adaptive focusing technique wasable to recover the spatial distribution of the phase aberrations. Totalacquisition time for 384 ultrasonic emission channels was 2 hours. Conclusion:Those first results in clinical MR at 1.5 T show that adaptive focusing of ahuman transcranial brain HIFU system can be achieved within reasonable timeunder MR guidance for aberrator layers as strong as human skull. Ongoing work isaiming at accelerating the acquisition in order to reach acceptable durationsfor in vivo protocols. © 2010 IEEE.
Motsclés: Acoustic Radiation Force Imaging; Adaptive focusing; brain; High Intensity FocusedUltrasound; MR guided therapy; Radiation Force; skull; Transcranial therapy; Acoustic Radiation Force Imaging; Adaptive focusing; High Intensity FocusedUltrasound; MR guided therapy; Radiation Force; skull; Transcranial; Acoustic emissions; Acoustic radiators; Acoustic wave propagation; Acoustic wave transmission; Experiments; Focusing; Tissue; Ultrasonic applications; Ultrasonics; Magnetic resonance


Mechanisms of attenuation and heating dissipation of ultrasound in the skull bone: Comparison between simulation models and experiments Pinton, G., M. Pernot, E. Bossy, J.F. Aubry, M. Muller, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 225228 (2010)
Résumé: Ultrasonic transmission measurements show that the ultrasound beam undergoes significant attenuation while propagating through the skull sample with values ranging from 12.6±1.33 dB. Simulations results indicate that scattering and mode conversion are responsible for the majority of the total acoustic attenuation (11.2 dB). Absorption of the skull at 1 MHz was determined to be 2 dB/cm for the compression wave and 4 dB/cm for the shear wave to match the experimental attenuation measurements. Based on this absorption value, temperature rises (up to 11.6°C) were numerically computed using the 3D thermal simulation and were in good agreement with the experimental infrared camera measurements. © 2010 IEEE.
Motsclés: 3d thermal simulation; Absorption values; Acoustic attenuation; Attenuation measurements; Compression waves; Infrared cameras; Mode conversions; Simulation model; Skull bone; Temperature rise; Transmission measurements; Ultrasound beams; Absorption; Shear flow; Three dimensional computer graphics; Ultrasonics; Computer simulation


Multiwave technology introducing shear wave elastography of the kidney: Preclinical study on a kidney fibrosis model and clinical feasibility study on 49 human renal transplants Gennisson, J.L., N. Grenier, R. Hubrecht, L. Couzy, Y. Delmas, M. Derieppe, S. Lepreux, P. Merville, A. Criton, J. Bercoff, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 13561359 (2010)
Résumé: Quantitative Increasing number of patients is affected by chronic kidney disease (CKD) world while with ensuing endstage renal disease (ESRD). A change in global approach to CKD from costly treatment of ESRD to more aggressive primary and secondary prevention is imperative. This improvement needs: a better understanding of mechanisms underlying renal scarring, a development of specific therapies to slow the progression and a development of modern diagnostic tools to characterize these underlying processes. Number of patients with ESRD underestimates CKD has probably exceeded by a factor 50 this last ten years due to initiation factors as hypertension, diabetes, hyperlipidemia, obesity or smoking. In this work, the Supersonic Shear Imaging technique (SSI) was proved to be able to provide a quantitative follow up of kidney fibrosis on rats. Then, the technique was adapted on curved probes and proposed to map the in vivo viscoelastic properties of human renal transplants and compared with biopsy. The SSI technique is based on the radiation force induced by a conventional ultrasonic probe, to generate a planar shear wave deep into tissues. Then shear wave propagation throughout the medium is caught in real time thanks to an ultrafast ultrasound scanner (5000 frames/s). At last, a time of flight algorithm applied on these data allows to compute a map of the shear wave velocity of the kidney. A follow up study of 8 weeks on a model of glomerulosclerosis induced by LName on 50 rats has been conducted in order to investigate the accuracy of the technique. Quantitative maps of the kidney cortex were performed with an 8 MHz linear probe. Regarding human renal transplants, quantitative maps of the cortex elasticity were produced for each patient with a 2.5 MHz curved array. In the animal study the results show an increase of the elasticity of the cortex of the kidney in time with a Young's modulus ranging from 9 to 25 kPa. Results are compared to histological measurement as proteinuria and or quantification of fibrosis with trichrome. On human renal transplants, three groups were studied: a control group, subjects with an early or with a late unfunctional transplant. The results obtained using a curved ultrasonic probe show an 8 cm depth by 10 cm width map of the Young's modulus for the 49 patients. Elasticity varies between groups from 9 to 50 kPa. Results were compared to histology and showed a good agreement between fibrosis markers and Young's modulus. Here we have demonstrated the feasibility of inducing shear waves using the supersonic shear imaging technique in vivo in rats and human kidneys. The good reproducibility and accuracy of the shear elasticity are discussed. The elasticity was proved to be clearly related to kidney fibrosis. As fibrotic process is responsible for the development of most CKD, noninvasive identification and followup of this process could improve renal prognosis if adapted targeted therapies can be applied. © 2010 IEEE.
Motsclés: kidney stiffness; kidney transplant; supersonic shear imaging; ultrafast ultrasonic imaging; Animal studies; Chronic kidney disease; Clinical feasibility; Control groups; Diagnostic tools; End stage renal disease; Follow up; Followup Studies; Glomerulosclerosis; Human kidney; Hyperlipidemia; Invivo; Initiation factors; kidney stiffness; Kidney transplants; Linear probe; Preclinical; Radiation forces; Real time; Renal transplants; Reproducibilities; Secondary prevention; Shear elasticity; Shea


Experimental reverse time migration for imaging of elasticity changes Arnal, B., M. Pernot, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 10391042 (2010)
Résumé: Recent studies have shown stiffness is an relevant tissue property tomonitor during High Intensity Focused Ultrasound (HIFU) treatments. Tissuestiffness is temperaturedependant but also a major indicator of thermalnecrosis. Shear Wave Imaging can be used to map stiffness changes in 2D, butcurrent inverse problem limits the spatial resolution and contrast of elasticitymaps. The aim of this study is to revisit the migration theory used ingeophysics for elasticity imaging [1]. Here, we demonstrate the feasibility of anew inverse problem of elastodynamics based on the experimental application ofReverse Time Migration (RTM) technique for the monitoring of elasticity changes.First, simulations have been performed using a 3D finite differences Virieuxscheme of the viscoelastic wave equation (ACEL). The propagation of elasticplane waves is investigated first in a reference homogeneous nonviscous mediumand secondly when adding a gaussian inclusion (3% to 60% shear wave speedcontrast). Here, the Tarantola's adjoint method [2][1] consists intimereversing the difference of the two successively generated shear waves(before and after heating) in the medium. The inversion is done bytimecorrelating the forward and the ad joint solution. Second, experiments wereperformed using a tungsten wire (125 m diameter) as a heating source in gelatinphantoms to decrease the local stiffness. The Supersonic Shear Imaging (SSI)technique gives access experimentally to the movie of 2D propagation of the wavebefore and while heating. Each wave was created by 3 pushing beams of 100s andtheir propagation was acquired at 10kHz using a commercial ultrasound scanner(Aixplorer, Supersonic Imagine) and a 8MHz probe. Acquisitions were performedevery 40s during 20min of heating and data were processed offline. RTM was ableto achieve inversion of shear wave propagation. We show that it can solve thisoptimization problem with a singleiteration in homogeneous media. This newmethod is more accurate than the timeofflight (TOF) inversion algorithm.Spatial resolution is improved (factor 2). Simulations and experimental resultsshow a very good recovery of the inclusion elasticity for different size andamplitude. © 2010 IEEE.
Motsclés: elastography; HIFU; migration; monitoring; shear wave; Adjoint methods; Different sizes; Elasticity imaging; Elastodynamics; Elastography; Experimental application; Finite difference; Gaussians; Heating source; HIFU; High intensity focused ultrasound; Homogeneous media; migration; Offline; Reverse time migrations; Shear wave imaging; Spatial resolution; Supersonic shear imaging; Time of flight; Tissue properties; Tungsten wires; Ultrasound scanners; Elasticity; Heating; Inverse problems; Proble


Evaluation of local arterial stiffness using ultrafast imaging: A comparative study using local arterial pulse wave velocity estimation and shear wave imaging Couade, M., C. Flanagan, W.N. Lee, E. Messas, M. Fink, M. Pernot, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 475478 (2010)
Résumé: We have previously proposed a novel method for measuring arterial stiffness using shear wave imaging (SWI). In this study, we evaluate the performance of this method on a healthy population (N30) and we compare it to local measurement of the arterial pulse wave velocity (PWV) achieved at the same arterial site using ultrafast imaging. Ultrafast imaging was used to track shear wave induced remotely by acoustic radiation force at the carotid site at a frame rate of 10000 images/second with a 8 MHz ultrasound probe. SWI was acquired with a repetition rate of 7 Hz in order to measure stiffness variation over the cardiac cycle. The axialvelocity field in the imaging plane was obtained using conventional Doppler algorithm. As shown in a previous study, acoustic radiation force applied normally to the arterial wall induces mainly a flexural guided mode (F0) which propagates between 100 to 1500 Hz. The dispersion curve of this mode is extracted from the 2DFFT of the shear wave spatiotemporal velocity field within and along the arterial wall. The shear modulus is then estimated by a theoretical fit of the experimental dispersion curve. Ultrafast imaging was also used to measure the tissue velocity of the arterial wall at the same site at a frame rate of 1000 images/s during 1 second. PWV was estimated by tracking the pulse wave along the arterial wall based on spatiotemporal velocity field at early and endsystole. Each ultrasound measurement was repeated 3 times on each carotid to estimate the reproducibility of the technique. Lower reproducibility was found on systolic PWV measurements. Thanks to its higher frequency content, the PWV at endsystole was measured more accurately and was found to be more reliable, but was not visible in all volunteers. In contrast, SWI offered high reproducibility. Moreover, arterial stiffness was achieved 6 times per seconds contrary to one time per second for PWV, giving access to the arterial stiffness time variation during the cardiac cycle. © 2010 IEEE.
Motsclés: Arterial stiffness; PWV; shear wave imaging; ultrafast imaging; Aframes; Acoustic radiation force; Arterial pulse; Arterial stiffness; Arterial wall; Cardiac cycles; Comparative studies; Dispersion curves; Doppler algorithms; Guided modes; Healthy population; High reproducibility; Higher frequencies; Imaging plane; Local measurement; Novel methods; Pulse wave; PWV; Repetition rate; Reproducibilities; shear wave imaging; Spatiotemporal; Stiffness variations; Time variations; ultrafast imaging;


Determination of the thickness  Plate velocity product of a plate structure with the green function comparison method Etaix, N., R.K. Ing, A. Leblanc, and M. Fink 17th International Congress on Sound and Vibration 2010, ICSV 2010 3, 22462252 (2010)
Résumé: Assuming the linearity of the Green's function with respect to the boundary conditions, it is demonstrated that the first antisymetric Lamb mode detected by a point receiver is proportional to that of a circular array of point receivers centred on it whatever location of the source and geometry of the plate. Therefore the Green function comparison method (GFCM) allows the determination of the plate velocity  thickness product from the measurement of ambient vibrations without using any emitter. Experimental results obtained with a plate of non regular geometry excited with a single transducer or a mobile loudspeaker kept in air are shown to validate theoretical approach. A second setup using a laser vibrometer to achieve the same measurements is realized for comparison purposes.
Motsclés: Ambient vibrations; Circular arrays; Comparison methods; Lamb modes; Laser vibrometers; Plate structure; Plate velocity; Regular geometry; Theoretical approach; Green's function; Vibrations (mechanical)


The DESAM toolbox: Spectral analysis of musical audio Lagrange, M., R. Badeau, B. David, N. Bertin, J. Echeveste, O. Derrien, S. Marchand, and L. Daudet 13th International Conference on Digital Audio Effects, DAFx 2010 Proceedings (2010)
Résumé: In this paper is presented the DESAM Toolbox, a set of Matlab functions dedicated to the estimation of widely used spectral models for music signals. Although those models can be used in Music Information Retrieval (MIR) tasks, the core functions of the toolbox do not focus on any specific application. It is rather aimed at providing a range of stateoftheart signal processing tools that decompose music files according to different signal models, giving rise to different "midlevel" representations. After motivating the need for such a toolbox, this paper offers an overview of the overall organization of the toolbox, and describes all available functionalities.
Motsclés: Core functions; Matlab functions; Music files; Music information retrieval; Music signals; Musical audio; Signal models; Spectral models; Signal processing; Spectrum analysis; Audio acoustics


Hybrid coding/indexing strategy for informed source separation of linear instantaneous underdetermined audio mixtures Parvaix, M., L. Girin, L. Daudet, J. Pinel, and C. Baras 20th International Congress on Acoustics 2010, ICA 2010  Incorporating Proceedings of the 2010 Annual Conference of the Australian Acoustical Society 5, 39873994 (2010)
Résumé: We present a system for underdetermined source separation of nonstationary audio signals from a stereo 2channel linear instantaneous mixture. This system is dedicated to isolate the different instruments/voices of a piece of music, so that an enduser can separately manipulate those source signals. The problem is addressed with a specific informed approach, that is implemented with a coder corresponding to the step of music production, and a separate decoder corresponding to the step of signal restitution. At the coder, source signals are assumed to be available, and are used to i) generate the stereo 2channel mix signal, and ii) extract a small amount of distinctive features embedded into the mix signal using an inaudible watermarking technique. At the decoder, extracting and exploiting the watermark from the transmitted mix signal enables an enduser who has no direct access to the original source signals to separate these source signals from the mix signal. In the present study, we propose a new hybrid system that merges two techniques of informed source separation: a subset of the source signals are encoded using a "sourceschannel coding" approach, and another subset are selected for local inversion of the mixture. The respective codes and indexes are transmitted to the decoder using a new highcapacity watermarking technique. At the decoder, the encoded source signals are decoded and then subtracted from the mixture signal, before local inversion of the remaining submixture signal leads to the estimation of the second subset of source signals. This hybrid separation technique enables to efficiently combine the advantages of both coding and inversion approaches. We report experiments with 5 different source signals separated from stereo mixtures, with a remarkable quality, enabling separate manipulation during music restitution.
Motsclés: Audio signal; End users; Highcapacity; Hybrid coding; Instantaneous mixtures; Mixture signals; Music production; Nonstationary; Separation techniques; Source signals; Underdetermined; Watermarking techniques; Audio watermarking; Hybrid systems; Separation; Signal analysis; Mixtures


Mathematical modeling in photoacoustic imaging of small absorbers Ammari, H., E. Bossy, V. Jugnon, and H. Kang SIAM Review 52, no. 4, 677695 (2010)
Résumé: This paper is devoted to mathematical modeling in photoacoustic imaging of small absorbers. We propose a new method for reconstructing small absorbing regions inside a bounded domain from boundary measurements of the induced acoustic signal. We also show the focusing property of the backpropagated acoustic signal. Indeed, we provide two different methods for locating a targeted optical absorber from boundary measurements of the induced acoustic signal. The first method consists of a MUltiple SIgnal Classification (MUSIC)type algorithm and the second one uses a multifrequency approach. We also show results of computational experiments to demonstrate efficiency of the algorithms. © 2010 Society for Industrial and Applied Mathematics.
Motsclés: Asymptotic expansion; Multifrequ ency imaging approach; MUSIC algorithm; Optical tomography; Photoacoustic imaging; Reconstruction algorithm; Small absorbers; Wave equation; Asymptotic expansion; Multifrequ ency imaging approach; MUSIC algorithm; Photoacoustic imaging; Reconstruction algorithm; Small absorbers; Acoustic signal processing; Acoustic waves; Algorithms; Asymptotic analysis; Computer music; Computer simulation; Optical tomography; Photoacoustic effect; Wavelet analysis; Computationa


In vivo soft tissues elasticity during thermal therapy is linked to the thermal dose SapinDebrosses, E., M. Pernot, M. Fink, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 455458 (2010)
Résumé: Increasing interest is given to elasticity to monitor HIFU treatments, since elasticity changes during thermal ablation. Moreover, the shear modulus of in vitro soft tissue samples was proven to be linked to the thermal dose. Hence, the study aims to evaluate the link of in vivo elasticity changes, assessed by supersonic shear imaging, with temperature and thermal dose. Seven male rats (Sprague Dawley, 250 g) were anesthetized. The right leg was depilated and immersed in a thermoregulated bath. Two optical temperature sensors were placed into the biceps femoris. The leg was warmed at a targeted temperature, from 38C to 50C, for a time corresponding to the theoretical threshold of necrosis in muscle (thermal dose 240 minutes at 43C). Every 40 seconds, shear plane waves were created in the biceps femoris, in a plane neighboring the thermocouples, using the Supersonic Shear Imaging method based on the radiation force. The shear wave propagation was acquired with 180 images at 10 000 frames/s. The changes of elasticity were assessed for the different temperaturetime profiles in order to highlight its dependence with the thermal dose. The leg swelled when the temperature reached 39C. Then, contraction of the muscular fibers was observed on the Bmode images at 4445C (thermal dose from 2 to 140 min), followed by a flow of fluid around the muscle. The effect of the thermal dose on the in vivo elasticity of the muscles was the same for all the rats. The shear modulus exponentially increased at a thermal dose was equal to 220 78 min. The cumulative thermal dose did not significantly change when the shear modulus reached 2.5 fold the initial value or more. Thus, this threshold value (220 min) was assumed to be the threshold of necrosis. This value is consistent with the necrosis of the skin and the theoretical threshold of necrosis of muscular tissues (240 min). This study gives promising prospects for the use of the elasticity to monitor thermal effects on tissues. © 2010 IEEE.
Motsclés: Acoustic Radiation Force; Shear Wave Imaging; Soft tissue elasticity; Thermal effects; Thermal Therapy; Aplane; Athermal; Acoustic radiation force; Bmode images; Biceps femoris; Invitro; Invivo; Initial values; Male rats; Muscular tissues; Radiation forces; Shear plane; Shear Wave Imaging; Soft tissue; Soft tissue elasticity; Supersonic shear imaging; Temperaturetime profiles; Thermal ablation; Thermal dose; Thermal therapies; Elastic moduli; Histology; Muscle; Rating; Rats; Shear flow; Sh


High sensitivity brain angiography using Ultrafast Doppler Macé, E., G. Montaldo, M. Fink, M. Tanter, I. Cohen, and R. Miles Proceedings  IEEE Ultrasonics Symposium, 11941197 (2010)
Résumé: A new mode called Ultrafast Doppler based on the coherent compounding ofultrafast ultrasonic images is proposed for brain angiography. It is proved boththeoretically and experimentally on a trepanated rat that it increases by afactor 25 the sensitivity of Power Doppler images because both the number ofacquisitions for each pixel and the signaltonoise ratio (SNR) are increasedwith Ultrafast Doppler. High quality images of the rat brain vascularization arepresented, showing the ability of Ultrafast Doppler to detect flows in verysmall vessels. In clinics, this technique could be applied for high qualitybrain angiography of newborn babies through the fontanel. © 2010 IEEE.
Motsclés: brain angiography; sensitivity; Ultrafast Doppler; Doppler; High quality images; High sensitivity; Power Doppler; Rat brain; sensitivity; Signal to noise; Ultrafast; Ultrasonic images; Vascularization; Rats; Signal to noise ratio; Ultrasonic imaging; Ultrasonics; Angiography


In vivo study of cerebral ischemia using Shear Wave Imaging and Ultrafast Doppler Mace, E., G. Montaldo, M. Fink, M. Tanter, A. Martin, and B. Tavitian Proceedings  IEEE Ultrasonics Symposium, 15381541 (2010)
Résumé: A multimodal ultrasound imaging study of cerebral ischemia was performed on a rat model. Ischemia was obtained by the transient 2h occlusion of a cerebral artery and the lesion induced was imaged 1, 2, 4 and 7 days after the stroke. With Bmode imaging, the lesion was found to be hyperechogenic compared to normal brain tissue. With Shear Wave Imaging, the elasticity of the brain was measured showing that the ischemic lesion is softer than normal brain tissue and that its elasticity decreases significantly over time. With Ultrafast Doppler, the perfusion in the brain was measured showing that the lesion is hyperperfused compared to normal brain tissue with a peak two days after the occlusion. Ultrafast Doppler was also proved able to monitor the occlusion. Future work will focused on applying this multimodal study for ischemic lesions induced by apoxia on newborn babies through the fontanel. © 2010 IEEE.
Motsclés: Cerebral ischemia; Shear Wave Imaging; Ultrafast Doppler; BMode imaging; Brain tissue; Cerebral arteries; Cerebral ischemia; Doppler; Invivo; Multimodal; Rat model; Shear Wave Imaging; Ultrafast; Ultrafast Doppler; Ultrasound imaging; Brain; Elasticity; Shear waves; Tissue; Ultrasonic imaging; Ultrasonics; Shear flow


Photorefractive SPS acousto optic imaging in thick diffusing media at 790nm Farahi, S., G. Montemezzani, A. A. Grabar, J.P. Huignard, and F. Ramaz 2010 Photonics Global Conference, PGC 2010 (2010)
Résumé: Acoustooptic imaging is based on ultrasound modulation of multiply scattered light in thick media. We experimentally demonstrate the possibility to perform a selfadaptive wavefront holographic detection at 790 nm, within the optical therapeutic window where absorption of biological tissues is minimized. A highgain Tedoped Sn2P2S6 bulk crystal is used for this purpose. We image optical absorbing objects embedded within a thick scattering phantom by use of pulsed ultrasound to get a dynamic millimetric axial resolution. Our technique represents an interesting approach for breast cancer detection.
Motsclés: Acoustooptic imaging; Axial resolutions; Biological tissues; Breast cancer detection; Bulk crystals; Highgain; Multiply scattered light; Photorefractive; Pulsed ultrasounds; Selfadaptive; Ultrasound modulation; Light scattering; Photonics; Ultrasonics; Ultrasonic applications


Waves around almost periodic arrangements of scatterers: Analysis of positional disorder Martin, P. A., and A. Maurel Mathematical Methods in the Applied Sciences 33, no. 18, 22152224 (2010)
Résumé: Much is known about the propagation of waves through periodic arrangements of identical scatterers, such as through a photonic crystal. Here, we consider a simple realization: scalar waves through a regular twodimensional array of identical small circles. We are interested in the effect of random disorder: the circles remain identical, but their centres are given small random displacements. We derive asymptotic approximations that can be used to quantify the effect of positional disorder. Extension to more complicated problems seems feasible and is expected. Copyright © 2010 John Wiley & Sons, Ltd.
Motsclés: acoustics; photonic crystals; QCA; Almost periodic; Asymptotic approximation; Positional disorder; QCA; Random disorders; Random displacement; Scalar waves; Twodimensional arrays; Photonic crystals


Musical instrument identification using multiscale melfrequency cepstral coefficients Sturm, B. L., M. Morvidone, and L. Daudet European Signal Processing Conference, 477481 (2010)
Résumé: We investigate the benefits of evaluating Melfrequency cepstral coefficients (MFCCs) over several time scales in the context of automatic musical instrument identification for signals that are monophonic but derived from real musical settings. We define several sets of features derived from MFCCs computed using multiple time resolutions, and compare their performance against other features that are computed using a single time resolution, such as MFCCs, and derivatives of MFCCs. We find that in each task  pairwise discrimination, and one vs. all classification  the features involving multiscale decompositions perform significantly better than features computed using a single timeresolution. © EURASIP, 2010.
Motsclés: Melfrequency cepstral coefficients; Multiscale Decomposition; Multiscales; Musical instrument identification; Musical setting; Time resolution; Timescales; Signal processing; Decomposition


How sparsely can a signal be approximated while keeping its class identity? Moussallam, M., T. Fillon, G. Richard, and L. Daudet MML'10  Proceedings of the 3rd ACM International Workshop on Machine Learning and Music, Colocated with ACM Multimedia 2010, 2528 (2010)
Résumé: This paper explores the degree of sparsity of a signal approximation that can be reached while ensuring that a sufficient amount of information is retained, so that its main characteristics remains. Here, sparse approximations are obtained by decomposing the signals on an overcomplete dictionary of multiscale timefrequency "atoms". The resulting representation is highly dependent on the choice of dictionary, decomposition algorithm and depth of the decomposition. The class identity is measured by indirect means as the speech/music discrimination power of features derived from the sparse representation compared to those of classical PCMbased features. Evaluation is performed on French Broadcast TV and Radio recordings from the QUAERO project database with two different statistical classifiers.
Motsclés: Algorithms; Experimentation; Amount of information; Broadcast TV; Decomposition algorithm; Experimentation; Main characteristics; Multiscales; Overcomplete dictionaries; Project database; Signal approximation; Sparse approximations; Sparse representation; Speech/music discrimination; Statistical classifier; Time frequency; Classification (of information); Learning systems; Speech recognition; Algorithms


Comparison between 1D transient elastography and Supersonic Shear Imagingtechnique: Application to the arterial wall elasticity assessment Brum, J., N. Benech, C. Negreira, J.L. Gennisson, M. Fink, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 13361339 (2010)
Résumé: Early detection of biomechanical modifications in the arterial wall couldbe used as a predictor factor for various diseases, for example hypertension oratherosclerosis. In this work 1D transient elastography (TE) technique andSupersonic Shear Imaging (SSI) technique are used for the evaluation of theshear wave speed on a phantom consisting in 2.5 mm thickness viscoelastic layerand an arterial phantom embedded in gel. In the TE technique the polarization ofthe shear wave is parallel to its propagation and the true shear wave speed isretrieved. In that case the dispersion is mainly due to viscosity (Voigt'smodel). Regarding the SSI technique, the dispersion is due to the layerthickness being of the order of the shear wavelength: thus the shear wave isguided as a Lamb wave. In that case a model is needed in order to retrieve theshear wave speed from the dispersion curve. Finally through both techniquessimilar shear wave speed estimations are obtained. © 2010 IEEE.
Motsclés: arterial wall; elastography; shear wave propagation; Arterial wall; Dispersion curves; Early detection; Elastography; Lamb Wave; Shear wave speed; Shear wave speed estimation; Transient elastography; Wave speed; Biomechanics; Dispersion (waves); Elasticity; Shear waves; Ultrasonics; Wave propagation; Shear flow


Reconstruction of membrane vibrations by the Wave Superposition Approach Leblanc, A., and R.K. Ing 17th International Congress on Sound and Vibration 2010, ICSV 2010 5, 34143421 (2010)
Résumé: Proceeding from the classical fundamental solution (Green's function) of membrane equation, the Wave Superposition Approach (WSA) allows the reconstruction of impulse responses by a set of virtual sources surrounding an original source. While only the free space vibration is used to obtain the virtual sources strengths, thanks to a matrix inversion, the solution implicitly satisfies any linear boundary conditions. The domain of validity of the method could be extended until close to the receiver location, thus maximizing the reconstruction area if the sensor is fixed near the edge of the membrane. Nevertheless, a particular attention must be paid on the numerical aspects of the WSA. Firstly, when the sources define a regular contour, additional sources must be used to ensure the uniqueness of the solution provided by the method. Secondly, the illconditioning of the monopole matrix to invert involves using a TSVD procedure. The setup used to apply the WSA consists in a laser vibrometer to measure normal velocities of the plate, and a piezoelectric disc for membrane excitation. The reciprocity principle is used to determine the velocities at virtual source locations and to obtain the experimental impulse response of the original source at the sensor location. Using analogy between membranes and thin plates submitted to simply supported boundary conditions, two applications of the WSA are shown for a rectangular glass plate and a complexshaped inox plate. High levels of correlations are achieved between the measured and the reconstructed impulses responses.
Motsclés: Free spaces; Fundamental solutions; Glass plate; Illconditioning; Laser vibrometers; Matrix inversions; Membrane vibrations; Numerical aspects; Piezoelectric disc; Receiver location; Reciprocity principle; Sensor location; Simply supported; Thin plate; Virtual sources; Wave superposition; Impulse response; Boundary conditions


Shear wave propagation in complex sub wavelength tissue geometries:Theoretical and experimental implications in the framework of cornea and skinshear wave imaging Nguyen, T.M., J.L. Gennisson, M. Couade, D. Touboul, P. Humbert, J. Bercoff, M. Fink, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 11451148 (2010)
Résumé: Quantitative measurements of cornea and skin biomechanical properties havemany applications in medicine. In ophthalmology, it could lead to a betterdiagnosis of pathologies or monitoring of treatments. In dermatology, it couldhelp the skin lesions removal monitoring. In the framework of Supersonic ShearImaging (SSI), these organs are characterized by their complex sub wavelengthgeometry (thin plate and thin capsule) that strongly influences the shear wavepropagation. In this work, a theoretical framework is proposed and validated inexperiments for the quantification of elastic modulus in these layered tissues.Shear wave dispersion induced by the guided propagation in such thin layers isestimated and fitted to the analytical dispersion curve derived from the leakyLamb Wave theory. SSI is refined and used in order to map in real time thetissues elasticity. This technique consists in generating a shear wave byultrasonic radiation force and imaging its propagation through the medium at ahigh frame rate (20 kHz). For infinite media the shear wave velocity is thenlinked to the Young's modulus. In cornea and skin layers, the highfrequencyshear wave (from 500 to 2000 Hz) is guided similarly to a Lamb wave, with platethickness (<1 mm) close to its wavelength. Experimental dispersion curveshave been confronted to numerical studies. First, finite differences simulationswere performed to obtain numerical dispersion curves in plates with exactlyknown thickness and elasticity. Besides, theoretical dispersion equations werederived by solving numerically the propagation equation. Dispersion curvesobtained in vitro on phantoms are found consistent with analytical calculations.Least mean squares fitting of curves enables to recover a quantitativeassessment of elasticity (standard deviation <10%). © 2010 IEEE.
Motsclés: cornea stiffness; Lamb waves; shear wave dispersion; skinstiffness; supersonic shear imaging; cornea stiffness; Lamb Wave; shear wave dispersion; skinstiffness; Supersonic shear imaging; Biomechanics; Curve fitting; Dermatology; Dispersions; Elastic moduli; Elasticity; Monitoring; Shear flow; Shear waves; Tissue; Ultrasonic waves; Ultrasonics; Wave propagation; Dispersion (waves)


Monitoring of thermal ablation therapy based on shear modulus changes:Shear wave thermometry and shear wave lesion imaging Arnal, B., M. Pernot, and M. Tanter Proceedings  IEEE Ultrasonics Symposium, 15221525 (2010)
Résumé: The use of High intensity Focused Ultrasound (HIFU) for non invasivetherapy requires improving realtime monitoring of the lesion formation duringtreatment, to avoid damage of the surrounding healthy tissues. The goal of thisstudy is to show the feasibility of a full ultrasound approach that relies onthe realtime and quantitative assessment of the changes in tissue elasticityboth to map temperature and monitor the lesion formation. HIFU treatment andmonitoring was performed using a confocal set made up of a 8MHz ultrasounddiagnostic probe (Vermon) and a 2.5MHz single element transducer focused at 30mm(Imasonic) on exvivo samples. UStemperature estimation based on speckletracking was combined with Supersonic Shear Wave Imaging (SWI) on the samedevice (Aixplorer, SuperSonic Imagine). The SWI sequence consisted in successiveshear waves induced at different lateral positions. The shear wave propagationwas acquired at 17000 frames/s, from which the elasticity map was recovered.HIFU sonications were interleaved with fast imaging acquisitions allowing a dutycycle of more than 90%. A lowtemperature elevation calibration phase isperformed using a dedicated sequence just before the actual treatment. A fullelasticity and temperature mapping was achieved every 3 seconds during thetreatment. Below 40C, tissue stiffness was found to reversibly decrease withtemperature at the focal zone (0.86kPa/°C). UStemperature washighlycorrelated to stiffness variation maps (correlation coefficient:0.910.97). The linear dependence of elasticity changes below 50°C enablesto perform thermometry imaging directly from elasticity changes maps. Then, forhigher temperatures, lesion formation induced a very strong increase of theelastic modulus in the focal zone. Thus, the same method allowed a completefollowup of the tissue during treatment in two particular regimes: shear wavethermometry during heating and shear wave lesion imaging when the thermalthreshold was reached. Shear wave temperature imaging allows temperature to beestimated up to 50°C. Moreover, SWT was shown to be very low sensitive tomotion (for tissue motion less than 2 cm/s) allowing temperature estimation onmoving area. Finally, the size of the thermal lesions determined on thestiffness maps correlated strongly with optical contrast of tissue cuts(/0.15mm). Shear Wave Thermometry is a novel reliable approach for ultrasoundbased monitoring of thermal ablation. SWT can be combined with shear wave lesionimaging to achieve a complete follow up of the treatment. © 2010 IEEE.
Motsclés: elastography; HIFU; rf ablation; thermometry; Correlation coefficient; Duty cycles; Elastography; Exvivo; Fast imaging; Focal zones; Follow up; Healthy tissues; HIFU; High intensity focused ultrasound; Lesion formation; Linear dependence; Low temperatures; Optical contrast; Quantitative assessments; Real time monitoring; rf ablation; Shear wave imaging; Single element transducers; Stiffness variations; Temperature estimation; Temperature imaging; Temperature mapping; Thermal ablation; Thermal l


Impact of clutter levels on spatial covariance: Implications for imaging Pinton, G. F., J. Dahl, and G. Try Proceedings  IEEE Ultrasonics Symposium, 21712174 (2010)
Résumé: The Van CittertZernike (VCZ) theorem describes the spatial covariance ofan incoherent source, such as the ultrasonic signal that is backscattered bytissue. A simulation tool that describes acoustic propagation, includingmultiple scattering and nonlinear propagation is used to characterize the effectof tissue structure on the spatial covariance. Simulated spatial covariancecurves are compared to in vivo data. It is shown that the nonrandom structureof tissue fundamentally modifies the spatial covariance function. Thereverberating echoes generated by the tissue layer add a decorrelated componentto the backscattered signal. It is shown that this decorrelation of the shortlag spatial covariance (SLSC) can provide a source of contrast to generateultrasound images at the fundamental and harmonic frequencies. Images ofanechoic lesions show that SLSC imaging has better contrast and boundarydefinition the Bmode images generated from the same echoes. © 2010 IEEE.
Motsclés: Acoustic propagation; Bmode images; Backscattered; Backscattered signal; Decorrelations; Harmonic frequency; Invivo; Incoherent sources; Nonlinear propagation; Simulation tool; Spatial covariance; Tissue layers; Tissue structure; Ultrasonic signals; Tissue; Ultrasonics


The effects of image degradation on ultrasoundguided HIFU Dahl, J. J., G. E. Trahey, and G. F. Pinton Proceedings  IEEE Ultrasonics Symposium, 809812 (2010)
Résumé: Highintensity focused ultrasound (HIFU) has recently found a wide range ofapplications. In the case of ultrasoundguided HIFU, clutter andphaseaberration can degrade the image quality such that visualization of thetarget can be significantly diminished. In this case the quality of the HIFUintensity deposition can be unknown. We modeled an 8 cm, 1.5 MHz HIFU array anda 6 cm, 2.5 MHz imaging array with propagation of acoustic waves through ahistological characterization of the human abdominal layer using a nonlinear,fullwave simulation method. Modifications were made to the simulated medium inorder to assess the impact of the individual image degradation mechanisms onintensity. For small targets (5 mm diameter lesions), the addition of a 3 cmthick abdominal layer completely obscured the imaging target positioned at 5 cmdepth, however, the deposition of HIFU intensity was not significantly degraded.An average elongation of 0.5mm of the intensity distribution was produced withthe abdominal layer, and the location of the peak focal intensity movedapproximately 0.03mm laterally and 0.9 mm axially. The average peak focalintensity dropped 0.6dB compared to the homogeneous tissue case, despite thepresence of strong phase aberration and reverberation clutter. The intensitydistribution returned nearly to normal when the phase aberration effects wereremoved and remained relatively unchanged when reverberation clutter wasremoved. © 2010 IEEE.
Motsclés: Focal intensity; Fullwave simulations; High intensity focused ultrasound; Homogeneous tissues; Image degradation; Imaging arrays; Intensity distribution; Phase aberrations; Small targets; Acoustic wave propagation; Clutter (information theory); Degradation; Image quality; Reverberation; Tissue; Visualization; Ultrasonics


Acoustic modelling of a convex pipe adapted for digital waveguide simulation Mignot, R., T. Hélie, and D. Matignon 13th International Conference on Digital Audio Effects, DAFx 2010 Proceedings (2010)
Résumé: This work deals with the physical modelling of acoustic pipes for realtime simulation, using the "Digital Waveguide Network" approach and the horn equation. With this approach, a piece of pipe is represented by a twoport system with a loop which involves two delays for wave propagation, and some subsystems without internal delay. A wellknown form of this system is the "KellyLochbaum" framework, which allows the reduction of the computation complexity. We focus this work on the simulation of pipes with a convex profile. But, using the "KellyLochbaum" framework with the horn equation, two problems occur: first, even if the outputs are bound, some substates have their values which diverge; second, there is an infinite number of such substates. The system is then unstable and cannot be simulated as such. The solution of this problem is obtained with two steps. First, we show that there is a simple standard form compatible with the "Waveguide" approach, for which there is an infinite number of solutions which preserve the input/output relations. Second, we look for one solution which guarantees the stability of the system and which makes easier the approximation in order to get a lowcost simulation.
Motsclés: Acoustic modelling; Computation complexity; Digital waveguides; Infinite numbers; Input/output; Physical modelling; Real time simulations; Two delays; Waveguides


Magnetooptical control of förster energy transfer Vincent, R., and R. Carminati AIP Conference Proceedings 1291, 9396 (2010)
Résumé: We study dipoledipole energy transfer between an emitter and an absorber in the presence of a nanoparticle with an anisotropic dielectric response. We demonstrate that the presence of the nanoparticle modifies the Förster Resonant Energy Transfer (FRET), and we present a general framework to deal with systems involving a donoracceptor couple and a nanostructure. In the particular case of a magnetooptical nanoparticle, for which the anisotropy can be tuned by an external magnetic field, we compute the generalized FRET rate and discuss the orders of magnitude. We show that the distance dependence can be different from the R 6 law of standard FRET. © 2010 American Institute of Physics.
Motsclés: Fluorescence; FRET; Magnetooptics; Nanoparticle; Quenching.; Single molecule


Nearfield interactions and fluctuations of the local density of states in a strongly scattering environment Pierrat, R., A. Cazé, and R. Carminati AIP Conference Proceedings 1291, 8587 (2010)
Résumé: We study the local density of states (LDOS) statistics near a dipole emitter embedded in a strongly scattering medium. We perform numerical simulations that emphasize the fact that LDOS fluctuations are strongly affected by the local environment of the emitter and is very sensitive to nearfield interactions and correlation of disorder. © 2010 American Institute of Physics.
Motsclés: Local density of states; Nearfield; Strongly scattering medium


Injection of midinfrared surface plasmon polaritons with an integrated device Tetienne, J.P., A. Bousseksou, D. Costantini, R. Colombelli, A. Babuty, I. MoldovanDoyen, Y. De Wilde, C. Sirtori, G. Beaudoin, L. Largeau, O. Mauguin, and I. Sagnes Applied Physics Letters 97, no. 21 (2010)
Résumé: We demonstrate a compact, integrated device in which surface plasmon polaritons (SPPs) are injected into a passive metal waveguide. We directly excite a SPP mode at a metalair interface using a roomtemperature midinfrared quantum cascade laser which is integrated onto the microchip. The SPP generation relies on endfire coupling and is demonstrated via both farfield and nearfield imaging techniques in the midinfrared. On one hand, a metallic diffraction grating is used to scatter in the farfield a portion of the propagating SPPs, thus allowing their detection with a microbolometer camera. On the other hand, direct images of the generated SPPs in the nearfield were collected with a scanning optical microscope. © 2010 American Institute of Physics.
Motsclés: Endfire coupling; Farfield; Integrated device; Metalair interface; Metallic diffraction; Microbolometer; Midinfrared quantum cascade; Midinfrared; Near field imaging; Nearfield; Passive metals; Room temperature; Scanning optical; Surface plasmon polaritons; Imaging techniques; Phonons; Photons; Plasmons; Quantum cascade lasers; Quantum theory; Solids; Waveguides; Surface plasmon resonance


Exploring shot noise and Laser Doppler imagery with heterodyne holography Gross, M., F. Verpillat, F. Joud, and M. Atlan 2010 9th EuroAmerican Workshop on Information Optics, WIO 2010 (2010)
Résumé: Heterodyne Holography is a variant of Digital Holography, where the optical frequencies of signal and reference arms can be freely adjusted by acoustooptic modulators. Heterodyne Holography is an extremely versatile and reliable holographic technique, which is able the reach the shot noise limit in sensitivity at very low levels of signal. Frequency tuning enables Heterodyne Holography to become a Laser Doppler imaging technique that is able to analyze various kinds of motion. © 2010 IEEE.
Motsclés: Acoustooptic modulator; Digital holography; Frequencytuning; Heterodyne holography; Holographic technique; Laser doppler; Laser Doppler imaging; Low level; Noise limit; Optical frequency; Classifiers; Computer generated holography; Doppler effect; Heterodyning; Imaging techniques; Shot noise; Laser recording


Structured and incoherent parametric dictionary design Yaghoobi, M., L. Daudet, and M. E. Davies ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing  Proceedings, 54865489 (2010)
Résumé: A new dictionary selection approach for sparse coding, called parametric dictionary design, has recently been introduced. The aim is to choose a dictionary from a class of admissible dictionaries which can be presented parametrically. The designed dictionary satisfies a constraint, here the incoherence property, which can help conventional sparse coding methods to find sparser solutions in average. In this paper, an extra constraint will be applied on the parametric dictionaries to find a structured dictionary. Various structures can be imposed on dictionaries to promote a correlation between the atoms. We intentionally choose a structure to implement the dictionary using a set of filter banks. This indeed helps to implement the dictionarysignal multiplications more efficiently. The price we pay for the extra structure is that the designed dictionary is not as incoherent as unstructured parametric designed dictionaries. ©2010 IEEE.
Motsclés: Dictionary selection; Parametric dictionary design; Sparse approximation; Structured dictionary; Dictionary selection; Parametric dictionary design; Sparse approximations; Sparse coding; Structured dictionary; Filter banks; Signal processing; Design


Subpoissonian number differences in fourwave mixing of matter waves Jaskula, J.C., M. Bonneau, G. B. Partridge, V. Krachmalnicoff, P. Deuar, K. V. Kheruntsyan, A. Aspect, D. Boiron, and C. I. Westbrook Physical Review Letters 105, no. 19 (2010)
Résumé: We demonstrate subPoissonian number differences in fourwave mixing of BoseEinstein condensates of metastable helium. The collision between two BoseEinstein condensates produces a scattering halo populated by pairs of atoms of opposing velocities, which we divide into several symmetric zones. We show that the atom number difference for opposing zones has subPoissonian noise fluctuations, whereas that of nonopposing zones is well described by shot noise. The atom pairs produced in a dual number state are well adapted to subshotnoise interferometry and studies of EinsteinPodolskyRosentype nonlocality tests. © 2010 The American Physical Society.


Effective propagation in a onedimensional perturbed periodic structure: Comparison of several approaches Maurel, A., P. A. Martin, and V. Pagneux Waves in Random and Complex Media 20, no. 4, 634655 (2010)
Résumé: Acoustic scattering by an ensemble of scatterers whose positions are close to the positions of a periodic arrangement (with small and random perturbations in the position of each scatterer) is considered in one dimension. Three methods are compared to obtain the effective wavenumber of the coherent field. The first two methods, the quasicrystalline approximation (QCA) and the coherent potential approximation (CPA), give the exact Floquet solution in the periodic case. However, in a perturbed almost periodic configuration, they give different dispersion relations. These methods are compared to a perturbation approach and confronted with the results obtained from direct numerical calculations. It is shown that CPA is able to get the first correction to the Floquet dispersion relation due to the introduced perturbation, in agreement with the perturbation approach and with direct numerical results, while QCA is unable to get this correction. © 2010 Taylor & Francis.
Motsclés: Acoustic Scattering; Almost periodic; Coherent fields; Coherentpotential approximation; Dispersion relations; Floquet; Numerical calculation; Numerical results; One dimension; Perturbation approach; Random perturbations; Wave numbers; Dispersion (waves); Green's function; Numerical methods; Quantum theory; Scattering; Periodic structures


Flower patterns in drop impact on thin liquid films Lagubeau, G., M. A. Fontelos, C. Josserand, A. Maurel, V. Pagneux, and P. Petitjeans Physical Review Letters 105, no. 18 (2010)
Résumé: We describe experimentally the formation of a pattern for drop impacts on thin liquid films for a large range of impact parameters. Using the shallowwater approximation, we are able to explain the main mechanisms leading to these patterns: it consists in the linear instability of the selfsimilar axisymmetric radial solution of the equations. Agreement between the experiments and the theory is remarkably good, leading, in particular, to the prediction that the most unstable fold number scales like (We/h∞)2/7. © 2010 The American Physical Society.
Motsclés: Axisymmetric; Drop Impact; Fold number; Impactparameter; Linear instabilities; Radial solutions; Selfsimilar; Shallowwater; Thin liquid film; Liquid films; Drops


Fluctuations of the local density of states probe localized surface plasmons on disordered metal films Krachmalnicoff, V., E. Castanié, Y. De Wilde, and R. Carminati Physical Review Letters 105, no. 18 (2010)
Résumé: We measure the statistical distribution of the local density of optical states (LDOS) on disordered semicontinuous metal films. We show that LDOS fluctuations exhibit a maximum in a regime where fractal clusters dominate the film surface. These large fluctuations are a signature of surfaceplasmon localization on the nanometer scale. © 2010 The American Physical Society.
Motsclés: Disordered metals; Film surfaces; Fractal clusters; Local density; Local density of state; Localized surface plasmon; Nanometer scale; Optical state; Semicontinuous metal films; Statistical distribution; Surfaceplasmon; Metallic films; Plasmons; Optical data storage


Nearfield interactions and nonuniversality in speckle patterns produced by a point source in a disordered medium Cazé, A., R. Pierrat, and R. Carminati Physical Review A  Atomic, Molecular, and Optical Physics 82, no. 4 (2010)
Résumé: A point source in a disordered scattering medium generates a speckle pattern with nonuniversal features, giving rise to the socalled C0 correlation. We analyze theoretically the relationship between the C0 correlation and the statistical fluctuations of the local density of states, based on simple arguments of energy conservation. This derivation leads to a clear physical interpretation of the C0 correlation. Using exact numerical simulations, we show that C0 is essentially a correlation resulting from nearfield interactions. These interactions are responsible for the nonuniversality of C0 that confers to this correlation a huge potential for sensing and imaging at the subwavelength scale in complex media. © 2010 The American Physical Society.
Motsclés: Complex media; Disordered medium; Local density of state; Near field interactions; Nonuniversality; Numerical simulation; Physical interpretation; Point sources; Scattering medium; Sensing and imaging; Speckle patterns; Statistical fluctuations; Subwavelength scale; Ferroelectric materials; Speckle; Correlation methods


Pathmemory induced quantization of classical orbits Fort, E., A. Eddi, A. Boudaoud, J. Moukhtar, and Y. Couder Proceedings of the National Academy of Sciences of the United States of America 107, no. 41, 1751517520 (2010)
Résumé: A droplet bouncing on a liquid bath can selfpropel due to its interaction with the waves it generates. The resulting "walker" is a dynamical association where, at a macroscopic scale, a particle (the droplet) is driven by a pilotwave field. A specificity of this system is that the wave field itself results from the superposition of the waves generated at the points of space recently visited by the particle. It thus contains a memory of the past trajectory of the particle. Here, we investigate the response of this object to forces orthogonal to its motion. We find that the resulting closed orbits present a spontaneous quantization. This is observed only when the memory of the system is long enough for the particle to interact with the wave sources distributed along the whole orbit. An additional force then limits the possible orbits to a discrete set. The wavesustained path memory is thus demonstrated to generate a quantization of angular momentum. Because a quantumlike uncertainty was also observed recently in these systems, the nonlocality generated by path memory opens new perspectives.
Motsclés: Bouncing droplets; Landau quantization; Pilot wave; Waveparticle duality; article; flow kinetics; force; magnetic field; mathematical model; priority journal; rotation; velocity


Low temperature nearfield scanning optical microscopy of IR and THz surfaceplasmon quantum cascade lasers MoldovanDoyen, I., A. Babuty, A. Bousseksou, R. Colombelli, S. Grésillon, and Y. De Wilde Lasers and ElectroOptics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 (2010)
Résumé: We present the first scattering type nearfield scanning optical microscope operating at low temperature. This instrument is ideal to study infrared and terahertz QCLs combined with metallic photonic crystal resonators and surface plasmon waveguides. © 2010 Optical Society of America.
Motsclés: Low temperatures; Metallic photonic crystals; Nearfield scanning optical microscope; Surface plasmon waveguide; Surfaceplasmon; Tera Hertz; Photonic crystals; Plasmons; Quantum cascade lasers; Near field scanning optical microscopy


Imaging the 3D scattering pattern of plasmonic nanoantennas by heterodyne numerical holography Suck, S. Y., S. Collin, N. Bardou, Y. De Wilde, and G. Tessier Lasers and ElectroOptics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 (2010)
Résumé: Optical nanoantennas are studied by full field heterodyne numerical holography in total internal reflection. After a spectroscopic characterization, the 3D scattering pattern of gold nanodisc chains was measured for wavelengths in and out of resonance. © 2010 Optical Society of America.
Motsclés: Fullfield; Nanoantennas; Nanodiscs; Plasmonic; Scattering pattern; Spectroscopic characterization; Total internal reflections; Holography; Refractive index; Three dimensional; Heterodyning


A semiconductor device for surfaceplasmon generation Bousseksou, A., A. Babuty, J.P. Tetienne, I. MoldovanDoyen, G. Beaudoin, C. Sirtori, I. Sagnes, Y. De Wilde, and R. Colombelli Lasers and ElectroOptics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 (2010)
Résumé: We demonstrate a compact semiconductor laser device for generation and launching of surface plasmon into a passive waveguide at room temperature. Surfaceplasmons are generated electrically at a single frequency using a distributedfeedback quantum cascade laser in the midinfrared wavelengths, they are then launched in a passive metal strip and detected using an apertureless near field scanning optical microscope. © 2010 Optical Society Of America.
Motsclés: Distributedfeedback; Midinfrared wavelengths; Nearfield scanning optical microscope; Passive metals; Passive waveguides; Room temperature; Single frequency; Surface plasmons; Surfaceplasmon; Feedback; Lasers; Plasmons; Quantum cascade lasers; Semiconductor device manufacture; Semiconductor lasers; Strip metal; Infrared lasers


Measuring and exploiting the transmission matrix in optics Popoff, S. M., G. Lerosey, R. Carminati, M. Fink, A. C. Boceara, and S. Gigan Lasers and ElectroOptics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 (2010)
Résumé: We introduce a method to measure the transmission matrix of a complex medium. This matrix exhibits statistical properties in good agreement with random matrix theory and allows light focusing and imaging through the random medium. ©2010 IEEE.
Motsclés: Complex medium; Light focusing; matrix; Random matrix theory; Random medium; Statistical properties; Transmission matrix


Quantitative Assessment of Arterial Wall Biomechanical Properties Using Shear Wave Imaging Couade, M., M. Pernot, C. Prada, E. Messas, J. Emmerich, P. Bruneval, A. Criton, M. Fink, and M. Tanter Ultrasound in Medicine and Biology 36, no. 10, 16621676 (2010)
Résumé: A new ultrasoundbased technique is proposed to assess the arterial stiffness: the radiation force of an ultrasonic beam focused on the arterial wall induces a transient shear wave (~10 ms) whose propagation is tracked by ultrafast imaging. The large and highfrequency content (100 to 1500 Hz) of the induced wave enables studying the wave dispersion, which is shown experimentally in vitro and numerically to be linked to arterial wall stiffness and geometry. The proposed method is applied in vivo. By repeating the acquisition up to 10 times per second (theoretical maximal frame rate is ~100 Hz), it is possible to assess in vivo the arterial wall elasticity dynamics: shear modulus of a healthy volunteer carotid wall is shown to vary strongly during the cardiac cycle and measured to be 130 ± 15 kPa in systole and 80 ± 10 kPa in diastole. (Email: ). © 2010 World Federation for Ultrasound in Medicine & Biology.
Motsclés: Acoustic radiation force; Arterial stiffness; Elastography; Ultrasound; Vascular imaging; Acoustic radiation force; Arterial stiffness; Elastography; Ultrasound; Vascular imaging; Acoustic emissions; Acoustic radiators; Acoustic wave propagation; Acoustic wave transmission; Biomechanics; Shear waves; Stiffness; Ultrasonic testing; Ultrasonics; Shear flow; adult; animal experiment; arterial stiffness; artery compliance; artery wall; article; biomechanics; carotid artery; diastole; echography; hea


Theory of electromagnetic timereversal mirrors De Rosny, J., G. Lerosey, and M. Fink IEEE Transactions on Antennas and Propagation 58, no. 10, 31393149 (2010)
Résumé: The theory of monochromatic timereversal mirrors (TRM) or equivalently phase conjugate mirrors is developed for electromagnetic waves. We start from the fundamental timesymmetry of the Maxwell's equations. From this symmetry, a differential expression similar to the Lorentz reciprocity theorem is deduced. The radiating conditions on TRM are expressed in terms of 6dimension Green's functions. To predict the time reversal focusing on antenna arrays, a formalism that involves impedance matrix is developed. We show that antenna coupling can dramatically modify the focal spot. Especially, we observe, that in some circumstances, subwavelength focusing on a bidimensional array may arise. © 2010 IEEE.
Motsclés: Antenna arrays; diffraction; microwaves; phase conjugate mirrors; plasmonic; subwavelength focusing; timereversal; timesymmetry; Phase conjugate mirrors; Plasmonic; Subwavelength; Timereversal; timesymmetry; Antenna phased arrays; Diffraction; Electromagnetic waves; Electromagnetism; Focusing; Green's function; Maxwell equations; Mirrors; Plasmons; Radio waves; Antennas


Acoustic Sizing of an Ultrasound Contrast Agent Maresca, D., M. Emmer, P. L. M. J. Van Neer, H. J. Vos, M. Versluis, M. Muller, N. De Jong, and A. F. W. Van Der Steen Ultrasound in Medicine and Biology 36, no. 10, 17131721 (2010)
Résumé: Because the properties of ultrasound contrast agent populations after administration to patients are largely unknown, methods able to study them noninvasively are required. In this study, we acoustically performed a size distribution measurement of the ultrasound contrast agent Definity ®. Single lipidshelled microbubbles were insonified at 25 MHz, which is considerably higher than their resonance frequency, so that their acoustic responses depended on their geometrical cross sections only. We calculated the size of each microbubble from their measured backscattered pressures. The acoustic size measurements were compared with optical reference size measurements to test their accuracy. Our acoustic sizing method was applied to 88 individual Definity ® bubbles to derive a size distribution of this agent. The size distribution obtained acoustically showed a mean diameter (2.5 μm) and a standard deviation (0.9 μm) in agreement within 8% with the optical reference measurement. At 25 MHz, this method can be applied to bubble sizes larger than 1.2 μm in diameter. It was observed that similar sized bubbles can give different responses (up to a factor 1.5), probably because of shell differences. These limitations should be taken into account when implementing the method in vivo. This acoustic sizing method has potential for estimating the size distribution of an ultrasound contrast agent noninvasively. (Email: ). © 2010 World Federation for Ultrasound in Medicine & Biology.
Motsclés: Acoustic bubble sizing; Definity ®; High frequency; Single bubbles; Size distribution; Ultrasound contrast agent; Acoustic response; Backscattered; Bubble size; Cross section; Definity; High frequency; Invivo; Mean diameter; Microbubble; Microbubbles; Resonance frequencies; Single bubbles; Size distribution measurements; Size measurements; Standard deviation; Ultrasound contrast agent; Resonance; Size determination; Size distribution; Ultrasonic transmission; Ultrasonics; perflutren; accurac


Ultracompact and unidirectional metallic antennas Bonod, N., A. Devilez, B. Rolly, S. Bidault, and B. Stout Physical Review B  Condensed Matter and Materials Physics 82, no. 11 (2010)
Résumé: We investigate the angular redistribution of light radiated by a single emitter located in the vicinity of dipolar silver nanoparticles. We point out the fundamental role of the phase differences introduced by the optical path difference between the emitter and the particle and demonstrate that the polarizability of the metallic nanoparticle alone cannot predict the emission directionality. In particular, we show that collective or reflective properties of single nanoparticles can be controlled by tuning the distance of a single emitter at a λ/30 scale. These results enable us to design unidirectional and ultracompact nanoantennas composed of just two coupled nanoparticles separated by a distance achievable with biological linkers. © 2010 The American Physical Society.


Finite element analysis of normal pressure hydrocephalus: Influence of CSF content and anisotropy in permeability Shahim, K., J.M. Drezet, J.F. Molinari, R. Sinkus, and S. Momjian Applied Bionics and Biomechanics 7, no. 3, 187197 (2010)
Résumé: Hydrocephalus is a cerebral disease where brain ventricles enlarge and compress the brain parenchyma towards the skull leading to symptoms like dementia, walking disorder and incontinence. The origin of normal pressure hydrocephalus is still obscure. In order to study this disease, a finite element model is built using the geometries of the ventricles and the skull measured by magnetic resonance imaging. The brain parenchyma is modelled as a porous medium fully saturated with cerebrospinal fluid (CSF) using Biot's theory of consolidation (1941). Owing to the existence of bundles of axons, the brain parenchyma shows locally anisotropic behaviour. Indeed, permeability is higher along the fibre tracts in the white matter region. In contrast, grey matter is isotropic. Diffusion tensor imaging is used to establish the local CSF content and the fibre tracts direction together with the associated local frame where the permeability coefficients are given by dedicated formulas. The present study shows that both inhomogeneous CSF content and anisotropy in permeability have a great influence on the CSF flow pattern through the parenchyma under an imposed pressure gradient between the ventricles and the subarachnoid spaces. © 2010 Taylor & Francis.
Motsclés: Anisotropy; Biomechanics; Brain parenchyma; Finite element modelling; Hydrocephalus; Permeability; Biot's theory; Brain parenchyma; Brain ventricles; Cerebro spinal fluids; Diffusion tensor imaging; Finite element analysis; Finite element modelling; Finite element models; Grey matters; Hydrocephalus; Imposed pressure gradient; Local frame; Normal pressure hydrocephalus; Permeability; Permeability coefficients; Porous medium; Subarachnoid spaces; White matter; Anisotropy; Biomechanics; Brain; Mag


Realtime visualization of muscle stiffness distribution with ultrasound shear wave imaging during muscle contraction Shinohara, M., K. Sabra, J.L. Gennisson, M. Fink, and M. L. Tanter Muscle and Nerve 42, no. 3, 438441 (2010)
Résumé: A standalone ultrasound shear wave imaging technology has been developed to quantify and visualize Young's modulus distribution by remotely applying ultrasound radiation force and tracking the resulting microvibrations in soft tissues with ultrafast ultrasound imaging. We report the first preliminary data that detected the distribution of local muscle stiffness within and between resting and contracting muscles at different muscle lengths with this technology. This technique may assist clinicians in characterizing muscle injuries or neuromuscular disorders. © 2010 Wiley Periodicals, Inc.
Motsclés: Dorsiflexion; Elastography; Plantarflexion; Spasticity; Young's modulus; adult; article; case report; echography; human; human experiment; male; muscle contraction; muscle length; muscle stiffness; normal human; priority journal; ultrasound; Young modulus; Adult; Biomechanics; Elasticity Imaging Techniques; Humans; Knee; Male; Muscle Contraction; Muscle, Skeletal; Physical Stimulation; Posture; Vibration


Incorporating scale information with cepstral features: Experiments on musical instrument recognition Morvidone, M., B. L. Sturm, and L. Daudet Pattern Recognition Letters 31, no. 12, 14891497 (2010)
Résumé: We present two sets of novel features that combine multiscale representations of signals with the compact timbral description of Melfrequency cepstral coefficients (MFCCs). We define one set of features, OverCs, from overcomplete transforms at multiple scales. We define the second set of features, SparCs, from a signal model found by sparse approximation. We compare the descriptiveness of our features against that of MFCCs by performing two simple tasks: pairwise musical instrument discrimination, and musical instrument classification. Our tests show that both OverCs and SparCs improve the characterization of the global timbre and local stationarity of an audio signal than do mean MFCCs with respect to these tasks. © 2009 Elsevier B.V. All rights reserved.
Motsclés: Audio signal classification; Musical instrument recognition; Sparse decompositions; Timefrequency/timescale features; Audio signal; Audio signal classification; Cepstral features; Melfrequency cepstral coefficients; Multiple scale; Multiscale representations; Overcomplete; Signal models; Sparse approximations; Sparse decomposition; Stationarity; Audio acoustics; Instruments; Signal analysis; Speech recognition; Statistical tests; Wavelet transforms; Electronic musical instruments


Pattern recognition of nonspeech audio Aucouturier, J.J., and L. Daudet Pattern Recognition Letters 31, no. 12, 14871488 (2010)


Reflection and transmission by a slab with randomly distributed isotropic point scatterers Maurel, A. Journal of Computational and Applied Mathematics 234, no. 6, 18421850 (2010)
Résumé: The problem of how a wave propagates in an infinite medium filled with scatterers has revealed the notion of an effective medium: the mean wave propagates as in an homogeneous medium with complex index. Is this notion of an effective medium still valid when the scatterers are bounded in space? The problem is treated here for isotropic point scatterers. It is shown that (i) the waves propagate inside the slab with an effective wavenumber K being the same as that in an infinite medium, (ii) the reflection and transmission coefficients of the slab mainly behave as R≃(1eiKL)(kK)2k and T≃eiKL at leading order, (iii) the reflection and transmission coefficients of a single interface are related to R and T with the usual law of optics and (iv) the boundary conditions to be applied at the interface are the continuity of the field and its first derivative for isotropic scatterers. Finally, numerical experiments in one dimension show satisfactory agreement with the presented theory. © 2009 Elsevier B.V.
Motsclés: Multiple scattering; Random media; Reflection & transmission; Complex indices; Effective medium; First derivative; Homogeneous medium; Isotropic points; Leading orders; Numerical experiments; One dimension; Random media; Randomly distributed; Reflection and transmission; Reflection and transmission coefficients; Wave numbers; Multiple scattering; Random processes; Reflection


Ultrafast compound Doppler imaging: A new approach of Doppler flow analysis Montaldo, G., E. Macé, I. Cohen, J. Berckoff, M. Tanter, and M. Fink 2010 7th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2010  Proceedings, 324327 (2010)
Résumé: This work applies the concept of compounded plane wave transmissions at very high frames rates of some KHz for ultrafast Doppler analysis over a large region of interest. As this compound imaging method has a similar quality to the standard focusing method but is 10 times faster, it is possible to generate fast Doppler images at frame rates of 300Hz. This frame rate is able to visualize transient phenomena and to display duplex modes with simultaneous color and spectrum analysis for each pixel of the image. The interest of the method is not restricted to high velocity flows; by optimizing the quality of the ultrasonic compounded image, it is possible to image very small velocity flows. This method is applied to a functional imaging of the rat brain by detecting changes in the flow after a drug injection. ©2010 IEEE.
Motsclés: Brain imaging; Doppler; Ultrasound; Brain imaging; Compound imaging; Doppler; Doppler analysis; Doppler images; Doppler imaging; Doppler ultrasound; Drug injection; Duplex modes; Flow analysis; Frame rate; Functional imaging; Highvelocity flows; Large regions; New approaches; Planewave transmission; Rat brain; Transient phenomenon; Ultrafast; Velocity flow; Doppler effect; Medical imaging; Spectrum analysis; Spectrum analyzers; Ultrasonics


In vivo brain elasticity mapping in small animals using ultrasound and its application to cerebral ischemia Macé, E., I. Cohen, A. Martín, G. Montaldo, M. Fink, B. Tavitian, and M. Tanter 2010 7th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2010  Proceedings, 245248 (2010)
Résumé: Shear Wave Imaging (SWI) is an ultrasound based technique for elasticity imaging that has been successfully tested on several organs in the framework of cancer diagnosis. In this work, the potential of this technique to map brain elasticity in vivo on trepanned small animals is investigated. From a SWI scan of the rat brain, 3D elasticity maps are reconstructed reaching a spatial resolution of 800 μm. The dynamic modulus of the brain tissues exhibits values in the 1 to 16 kPa range and is quantified for different anatomical regions. The propagation of shear waves is found to be anisotropic, which could be a consequence of fiber orientation. Finally, the interest of brain elasticity mapping for the monitoring of brain ischemia is investigated on a rat model. Focal cerebral ischemia is shown to induce a dramatic decrease of elasticity in the lesion. ©2010 IEEE.
Motsclés: Brain elasticity; Cerebral ischemia; Shear wave imaging; Small animal; 3D elasticity; Anatomical regions; Brain ischemia; Brain tissue; Cancer diagnosis; Cerebral ischemia; Dynamic moduli; Elasticity imaging; Fiber orientations; Invivo; Rat brain; Rat model; Shear wave imaging; Small Animal; Spatial resolution; Animals; Elasticity; Medical imaging; Shear flow; Shear waves; Three dimensional; Ultrasonic applications; Ultrasonics; Brain


Dynamic and quantitative assessment of myocardial stiffness using shear wave imaging Pernot, M., M. Couade, P. Mateo, R. Fischmeister, B. Crozatier, and M. Tanter 2010 7th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2010  Proceedings, 976979 (2010)
Résumé: Shear Wave Imaging was used to assess the myocardial stiffness in Langendorff perfused rat heart. This technique was used to quantify the myocardial stiffness and its dynamics over the cardiac cycle. This method is based on the generation of a shear wave (typically in the kHz range) that propagates in soft tissues at a velocity of a few meters per second that is linked to the tissue stiffness. The acquisition of the shear wave propagation was performed in less than 10 ms, enabling the possibility to follow dynamically the variation of the myocardial stiffness during the cardiac cycle. The feasibility of imaging the myocardial elasticity was demonstrated up to 15 times per cardiac cycle. The mean shear wave velocity was found to be 3.8 ± 0.6 m/s in the systolic phase and 1.1 ± 0.15 m/s in the diastolic phase when the probe was set in the long axis orientation. © 2010 IEEE.
Motsclés: Cardiac imaging; Elasticity imaging; Elastography; Myocardial stiffness; Radiation force; Shear wave; Cardiac imaging; Elasticity imaging; Elastography; Radiation force; Radiation forces; Elasticity; Heart; Medical imaging; Shear waves; Stiffness; Ultrasonic devices; Wave propagation; Shear flow


Compressed sensing for digital holographic microscopy Marim, M. M., M. Atlan, E. D. Angelini, and J.C. OlivoMarin 2010 7th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2010  Proceedings, 684687 (2010)
Résumé: This paper describes an original microscopy imaging framework successfully employing Compressed Sensing for digital holography. Our approach combines a sparsity minimization algorithm to reconstruct the image and digital holography to perform quadratureresolved random measurements of an optical field in a diffraction plane. Compressed Sensing is a recent theory establishing that nearexact recovery of an unknown sparse signal is possible from a small number of nonstructured measurements. We demonstrate with practical experiments on holographic microscopy images of cerebral blood flow that our CS approach enables optimal reconstruction from a very limited number of measurements while being robust to high noise levels. © 2010 IEEE.
Motsclés: Biological microscopy; Compressed sensing; Digital holography; Signal reconstruction; Biological microscopy; Cerebral blood flow; Compressed sensing; Diffraction planes; Digital holographic microscopy; Digital holography; High noise levels; Holographic microscopy; Microscopy imaging; Minimization algorithms; Optical field; Random measurement; Sparse signals; Computer generated holography; Medical imaging; Optimization; Repair; Signal analysis; Signal reconstruction


Real time quantitative elastography using supersonic shear wave imaging Tanter, M., M. Pernot, G. Montaldo, J.L. Gennisson, E. Bavu, E. Macé, T.M. Nguyen, M. Couade, and M. Fink 2010 7th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2010  Proceedings, 276279 (2010)
Résumé: Supersonic Shear Imaging (SSI) is a quantitative stiffness imaging technique based on the combination of a radiation force induced in tissue by an ultrasonic beam and ultrafast ultrasound imaging sequence (up to more than 10000 frames per second) catching in real time the propagation of the resulting shear waves. Local shear wave speed is estimated and enables the two dimensional mapping of shear elasticity. This imaging modality is implemented on conventional probes driven by dedicated ultrafast echographic devices and can be performed during a standard ultrasound exam. The clinical potential of SSI is today extensively investigated for many potential applications such as breast cancer diagnosis, liver fibrosis staging, cardiovascular applications, ophthalmology. This invited lecture presents a short overview of the current investigated applications of SSI. ©2010 IEEE.
Motsclés: Cancer; Diagnosis; Elastography; Ultrafast imaging; Ultrasound; Breast cancer diagnosis; Cancer diagnosis; Cardiovascular applications; Elastography; Frames per seconds; Imaging modality; Liver fibrosis; Potential applications; Radiation forces; Real time; Shear elasticity; Shear wave imaging; Shear wave speed; Supersonic shear imaging; Two dimensional mapping; Ultrafast; Ultrafast imaging; Ultrasonic beams; Ultrasound imaging; Medical imaging; Shear waves; Ultrasonic testing; Ultrasonics; Shea


Silver square nanospirals mimic optical properties of Ushaped metamaterials Gallas, B., K. Robbie, R. Abdeddaïm, G. Guida, J. Yang, J. Rivory, and A. Priou Optics Express 18, no. 16, 1633516344 (2010)
Résumé: We present a study of the optical properties of threearmed square nanospirals made of silver and realized as nanostructured thin films with Glancing Angle Deposition. Calculation of current flows in the nanospirals show excited resonant modes resembling those observed in Ushaped resonators. Four principal resonances were determined: near 200 THz and 480 THz for one polarization and 250 THz and 650 THz for the polarization orthogonal to the first one. In particular, a mode with antiparallel current flow in opposite arms, associated with the observed resonance near 650 THz, indicates the existence of a magneticlike resonance in the square nanospiral arrays. The robustness of the resonances against variations in the structural parameters of the nanospirals was investigated. This study revealed that the main parameter driving the position of the resonances was the overall dimension of the nanospiral, directly related to the length of their arms. Optical properties of a sample were measured by generalized spectroscopic ellipsometry at nearnormal incidence, and evidence conversion between polarization states even for light polarized in the plane containing one of the arms in agreement with the numerical study. The measurements compared favorably to the results of the numerical simulations taking into account the disorder in the sample. © 2010 Optical Society of America.
Motsclés: Antiparallel currents; Current flows; Glancing Angle Deposition; Main parameters; Nanostructured thin film; Normal incidence; Numerical simulation; Numerical studies; Polarization state; Principal resonance; Resonant mode; Structural parameter; Ushaped; Deposition; Metamaterials; Polarization; Resonance; Silver; Spectroscopic ellipsometry; Optical properties; nanomaterial; silver; article; chemistry; computer simulation; equipment design; light; magnetism; radiation scattering; Computer Simula


MRguided adaptive focusing of ultrasound Larrat, B., M. Pernot, G. Montaldo, M. Fink, and M. Tanter IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 57, no. 8, 17341747 (2010)
Résumé: Adaptive focusing of ultrasonic waves under the guidance of a magnetic resonance (MR) system is demonstrated for medical applications. This technique is based on the maximization of the ultrasonic wave intensity at one targeted point in space. The wave intensity is indirectly estimated from the local tissue displacement induced at the chosen focus by the acoustic radiation force of ultrasonic beams. Coded ultrasonic waves are transmitted by an ultrasonic array and an MRI scanner is used to measure the resulting local displacements through a motionsensitive MR sequence. After the transmission of a set of spatially encoded ultrasonic waves, a noniterative inversion process is employed to accurately estimate the spatialtemporal aberration induced by the propagation medium and to maximize the acoustical intensity at the target. Both programmable and physical aberrating layers introducing strong distortions (up to 2π radians) were recovered within acceptable errors (<0.8 rad). This noninvasive technique is shown to accurately correct phase aberrations in a phantom gel with negligible heat deposition and limited acquisition time. These refocusing performances demonstrate a major potential in the field of MRguided ultrasound therapy in particular for transcranial brain highintensity focused ultrasound. © 2010 IEEE.
Motsclés: Acoustic radiation force; Acquisition time; Adaptive focusing; Heat deposition; High intensity focused ultrasound; Local displacement; MR sequence; MRI scanners; Noniterative; Noninvasive technique; Phase aberrations; Spatial temporals; Tissue displacement; Transcranial; Ultrasonic arrays; Ultrasonic beams; Ultrasound therapy; Wave intensities; Aberrations; Acoustic fields; Gels; Geometrical optics; Medical applications; Resonance; Scanning; Ultrasonic testing; Ultrasonic waves; Ultrasonics


Estimating the dynamic effective mass density of random composites Martin, P. A., A. Maurel, and W. J. Parnell Journal of the Acoustical Society of America 128, no. 2, 571577 (2010)
Résumé: The effective mass density of an inhomogeneous medium is discussed. Random configurations of circular cylindrical scatterers are considered, in various physical contexts: fluid cylinders in another fluid, elastic cylinders in a fluid or in another solid, and movable rigid cylinders in a fluid. In each case, timeharmonic waves are scattered, and an expression for the effective wavenumber due to Linton and Martin [J. Acoust. Soc. Am. 117, 34133423 (2005)] is used to derive the effective density in the low frequency limit, correct to second order in the area fraction occupied by the scatterers. Expressions are recovered that agree with either the Ament formula or the effective static mass density, depending upon the physical context. © 2010 Acoustical Society of America.
Motsclés: Area fraction; Effective density; Effective mass density; Elastic cylinders; Inhomogeneous medium; Low frequency limits; Mass densities; Random composites; Random configurations; Rigid cylinder; Second orders; Timeharmonic waves; Wave numbers; Fluids; Circular cylinders; acoustics; article; motion; pressure; statistical model; theoretical model; Young modulus; Acoustics; Elastic Modulus; Linear Models; Models, Theoretical; Motion; Pressure


Singular value distribution of the propagation matrix in random scattering media Aubry, A., and A. Derode Waves in Random and Complex Media 20, no. 3, 333363 (2010)
Résumé: The distribution of singular values of the propagation operator in a random medium is investigated, in a backscattering configuration. Experiments are carried out with pulsed ultrasonic waves around 3 MHz, using an array of 64 programmable transducers placed in front of a random scattering medium. The impulse responses between each pair of transducers are measured and form the response matrix. The evolution of its singular values with time and frequency is computed by means of a shorttime Fourier analysis. The mean distribution of singular values exhibits a very different behaviour in the single and multiple scattering regimes. The results are compared with random matrix theory. Once the experimental matrix coefficients are renormalized, experimental results and theoretical predictions are found to be in a very good agreement. Two kinds of random media have been investigated: a highly scattering medium in which multiple scattering predominates and a weakly scattering medium. In both cases, residual correlations that may exist between matrix elements are shown to be a key parameter. Finally, the possibility of detecting a target embedded in a random scattering medium based on the statistical properties of the strongest singular value is discussed. © 2010 Taylor & Francis.
Motsclés: Key parameters; Matrix coefficients; Matrix elements; Propagation matrix; Propagation operators; Pulsed ultrasonic wave; Random matrix theory; Random media; Random medium; Random scattering media; Random scattering medium; Residual correlation; Response matrices; Scattering medium; Singular values; Statistical properties; Theoretical prediction; Fourier analysis; Multiple scattering; Transducers; Ultrasonics


Thickness or phase velocity measurements using the Green's function comparison method Etaix, N., A. Leblanc, M. Fink, and R.K. Ing IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 57, no. 8, 18041812 (2010)
Résumé: The acoustic guided wave propagation for plate thickness measurement is generally treated in free space to simplify the formal approach. In this paper, propagation in a closed environment is treated by dealing with plates of finite dimensions and arbitrary geometries and linear boundary conditions. The present approach considers the plate Green's function to be composed of two terms. The first term corresponds to the Green's function of an infinite plate. The second term corresponds to a correction term which, in addition to the first term, satisfies all equations. Assuming the boundary conditions to be linear, it is found that the acoustic wave generated by a point source is proportional to that of a circular array of sources centered on it. By measuring the ratio between the two signals, either the plate velocity or plate thickness can be determined. This new method has been successfully applied to isotropic and anisotropic homogeneous plates of different geometries, on inhomogeneous plates, and also in a passive mode, without an active transmitter. © 2010 IEEE.
Motsclés: Arbitrary geometry; Circular arrays; Closed environment; Comparison methods; Different geometry; Finite dimensions; Formal approach; Free space; Guided wave propagation; Homogeneous plates; Infinite plate; Inhomogeneous plate; Passive mode; Plate thickness; Plate velocity; Point sources; Acoustic wave propagation; Acoustics; Boundary conditions; Guided electromagnetic wave propagation; Thickness measurement; Velocity measurement; Green's function


High impedance surfaces based antennas for high data rate communications at 40 ghz Tran, C. M., H. Hafdallah Ouslimani, L. Zhou, A. C. Priou, H. Teillet, J.Y. Daden, and A. Ourir Progress In Electromagnetics Research C 13, 217229 (2010)
Résumé: Millimeter wave High Impedance Surfaces (HIS) based antennas are designed, fabricated, and characterized for high data rate communications at frequencies around 40 GHz. HIS with different finite surface area sizes are used as a ground plane for the microstrip patch antennas to suppress the surface waves. The antenna measurements and full wave electromagnetic simulations demonstrate a wide bandwidth of 1215% in the frequency range of 3844 GHz with a high gain of ~6 dB and a very low cross polar contribution better than 20 dB.
Motsclés: Antenna measurement; Finite surface; Frequency ranges; Fullwave electromagnetic simulation; Ground planes; High data rate communications; High gain; High impedance surface; Highimpedance surfaces; Microstrip patch antennas; Polar contribution; Wide bandwidth; Surface waves; Antennas


Breast lesions: Quantitative elastography with supersonic shear imaging  Preliminary results Athanasiou, A., A. Tardivon, M. Tanter, B. SigalZafrani, J. Bercoff, T. Deffieux, J.L. Gennisson, M. Fink, and S. Neuenschwander Radiology 256, no. 1, 297303 (2010)
Résumé: Purpose: To determine the appearance of breast lesions at quantitative ultrasonographic (US) elastography by using supersonic shear imaging (SSI) and to assess the correlation between quantitative values of lesion stiffness and pathologic results, which were used as the reference standard. Materials and Methods: This study was approved by the French National Committee for the Protection of Patients Participating in Biomedical Research Programs. All patients provided written informed consent. Conventional US and SSI quantitative elastography were performed in 46 women (mean age, 57.6 years;age range, 3871 years) with 48 breast lesions (28 benign, 20 malignant;mean size, 14.7 mm);pathologic results were available in all cases. Quantitative lesion elasticity was measured in terms of the Young modulus (in kilopascals). Sensitivity, specifi city, and area under the curve were obtained by using a receiver operating characteristic curve analysis to assess diagnostic performance. Results: All breast lesions were detected at SSI. Malignant lesions exhibited a mean elasticity value of 146.6 kPa ± 40.05 (standard deviation), whereas benign ones had an elasticity value of 45.3 kPa ± 41.1 (P < .001). Complicated cysts were differentiated from solid lesions because they had elasticity values of 0 kPa (no signal was retrieved from liquid areas). Conclusion: SSI provides quantitative elasticity measurements, thus adding complementary information that potentially could help in breast lesion characterization with Bmode US. © RSNA, 2010.
Motsclés: adult; aged; article; B scan; breast biopsy; breast cancer; breast fibroadenoma; breast lesion; clinical article; controlled study; correlation analysis; diagnostic imaging; echomammography; elastography; female; fibrocystic breast disease; human; human tissue; image analysis; priority journal; quantitative diagnosis; sensitivity and specificity; Young modulus; Adult; Aged; Area Under Curve; Breast Neoplasms; Diagnosis, Differential; Elasticity Imaging Techniques; Female; Humans; Image Interpret


Progress on the strong Eshelby's conjecture and extremal structures for the elastic moment tensor Ammari, H., Y. Capdeboscq, H. Kang, H. Lee, G. W. Milton, and H. Zribi Journal des Mathematiques Pures et Appliquees 94, no. 1, 93106 (2010)
Résumé: We make progress towards proving the strong Eshelby's conjecture in three dimensions. We prove that if for a single nonzero uniform loading the strain inside inclusion is constant and further the eigenvalues of this strain are either all the same or all distinct, then the inclusion must be of ellipsoidal shape. As a consequence, we show that for two linearly independent loadings the strains inside the inclusions are uniform, then the inclusion must be of ellipsoidal shape. We then use this result to address a problem of determining the shape of an inclusion when the elastic moment tensor (elastic polarizability tensor) is extremal. We show that the shape of inclusions, for which the lower HashinShtrikman bound either on the bulk part or on the shear part of the elastic moment tensor is attained, is an ellipse in two dimensions and an ellipsoid in three dimensions. Nous progressons dans la résolution de la conjecture d'Eshelby en trois dimensions. En effet, nous démontrons que si pour un seul chargement uniforme (non trivial), le champ de contraintes dans une inclusion élastique est constant et de plus, si ses valeurs propres sont soit toutes les mêmes soit différentes les unes des autres alors l'inclusion est nécessairement de forme ellipsoïdale. Il en découle que si pour deux chargements uniformes, linéairement indépendants, les champs de contraintes sont constants alors l'inclusion doit être un ellipsoïde. Nous déterminons ensuite la forme d'une inclusion pour laquelle la borne inférieure de HashinShtrikman est atteinte soit par la partie compression soit par la partie cisaillement du moment élastique. Nous démontrons qu'il s'agit en fait d'une forme elliptique en dimension deux et d'une forme ellipsoïdale en dimension trois. © 2010 Elsevier Masson SAS.
Motsclés: 74B05; Elastic moment tensor; HashinShtrikman bounds; Newtonian potential; Strong Eshelby's conjecture


SiliconOnDiamond layer integration by wafer bonding technology Rabarot, M., J. Widiez, S. Saada, J.P. Mazellier, C. Lecouvey, J.C. Roussin, J. Dechamp, P. Bergonzo, F. Andrieu, O. Faynot, S. Deleonibus, L. Clavelier, and J. P. Roger Diamond and Related Materials 19, no. 79, 796805 (2010)
Résumé: In this study, SiliconOnDiamond (SOD) microstructures have been fabricated using either Smart Cut™ or bonded and EtchedBack Silicon On Insulator (BESOI) technology. Thanks to the development of an innovative smoothening process, polycrystalline diamond layers (C*) can be integrated as a buried oxide layer offering new opportunities in terms of thermal management. We describe different technological process flow investigations leading to SOD by bonding C* layer in the stack. As starting material we used polycrystalline thin diamond films in the 200 nm to 7000 nm range of thickness. The C* is deposited by Chemical Vapour Deposition assisted by Microwave Plasma (MPCVD) onto various 50 mm wafers such as Si, SOI and polycrystalline silicon carbide (pSiC). As the roughness of the diamond layer is not directly compatible with a wafer bonding integration, an innovative smoothening process in 3 steps has been developed and named "DPE" for Deposition, Planarization and Etching. Using the DPE process, the roughness of 5 μm thick diamond layer could be reduced from 50 to 3 nm RMS and down to 1.5 nm RMS for a thin 200 nm layer. In order to demonstrate the feasibility of a GaN on SOD microstructure design for HEMT applications, layer transfers have been carried out by a bonding and thinning process from C*/Si bulk using oxide bonding layers. From thermal spreading efficiency consideration, new processes of fabrication of SOD/polySiC substrate are in progress involving BESOI or Si Smart Cut™ technologies and polySi bonding layer starting from C*/polySiC. Pure SOD substrate were also fabricated by using C*/SOI and polySi bonding layer in a BESOI technology. A thin active silicon layer (70 nm) of 50 mm diameter onto a 140 nm thick diamond BOX layer has been transferred on 200 mm diameter Si substrate for future MOSFET's devices demonstrations. Significant progress has been done in diamond layer integration by wafer bonding. © 2010 Elsevier B.V. All rights reserved.
Motsclés: Diamond wafer bonding; DPE; Smoothening diamond process; SOD; Bonding layers; BOX layers; Buried oxide layers; Chemical vapour deposition; Diamond layers; Diamond wafer bonding; Diamond wafers; Layer transfer; Microwave plasma; MOSFET; New opportunities; New process; Planarization; PolySi; PolySic; Polycrystalline; Polycrystalline diamond layers; Polycrystalline silicon carbide; Si substrates; SiC substrates; Silicon layer; Silicon on insulator; Smartcut; Starting materials; Technological pr


Elasticity reconstruction: Beyond the assumption of local homogeneity Sinkus, R., J.L. Daire, B. E. Van Beers, and V. Vilgrain Comptes Rendus  Mecanique 338, no. 78, 474479 (2010)
Résumé: Elasticity imaging is a novel domain which is currently gaining significant interest in the medical field. Most inversion techniques are based on the homogeneity assumption, i.e. the local spatial derivatives of the complexshear modulus are ignored. This analysis presents an analytic approach in order to overcome this limitation, i.e. first order spatial derivatives of the realpart of the complexshear modulus are taken into account. Resulting distributions in a gauged breast lesion phantom agree very well with the theoretical expectations. An invivo example of a cholangiocarcinoma demonstrates that the new approach provides maps of the viscoelastic properties which agree much better with expectations from anatomy. © 2010 Académie des sciences.
Motsclés: Biomechanics; Complexshear modulus; Elasticity imaging; Inverse problems; Medical imaging; analytical method; anatomy; biomechanics; cancer; elasticity; homogeneity; imaging method; inverse problem; lesion; numerical model; reconstruction; shear modulus


Number of propagating modes of a diffusive periodic waveguide in the semiclassical limit Barra, F., A. Maurel, V. Pagneux, and J. Zuñiga Physical Review E  Statistical, Nonlinear, and Soft Matter Physics 81, no. 6 (2010)
Résumé: We study the number of propagating Bloch modes NB of an infinite periodic billiard chain. The asymptotic semiclassical behavior of this quantity depends on the phasespace dynamics of the unit cell, growing linearly with the wave number k in systems with a nonnull measure of ballistic trajectories and going like ∼√k in diffusive systems. We have calculated numerically NB for a waveguide with cosineshaped walls exhibiting strongly diffusive dynamics. The semiclassical prediction for diffusive systems is verified to good accuracy and a connection between this result and the universality of the parametric variation of energy levels is presented. © 2010 The American Physical Society.
Motsclés: Ballistic trajectories; Bloch modes; Diffusive dynamics; Diffusive system; Energy level; Parametric variation; Periodic waveguides; Phasespace dynamics; Propagating mode; Semiclassical limit; Unit cells; Wave numbers; Phase space methods; Waveguides


Theory of infrared nanospectroscopy by photothermal induced resonance Dazzi, A., F. Glotin, and R. Carminati Journal of Applied Physics 107, no. 12 (2010)
Résumé: We present a theoretical investigation of the physics involved in a recently developed spectromicroscopy technique, called photothermal induced resonance (PTIR). With this technique, one measures the local infrared absorption spectrum of a sample shined with a tunable infrared laser pulse, and detects the induced photothermal expansion with the tip of an atomic force microscope (AFM). Simple physical assumptions allow us to describe analytically the heating and expansion of the sample, the excitation of the vibration modes of the AFM cantilever, and the detected signal. We show that the signal depends on the thermal expansion velocity rather than on the absolute displacement of the tip, and we investigate the influence of the laser pulse length. Eventually, we express the PTIR signal in terms of relevant parameters, and prove its proportionality to the sample absorbance. This analytical approach complement our experimental results and validates the PTIR method as a technique of choice for infrared spectroscopy of nanoscopic samples, getting around optical artifacts like reflectance perturbation. © 2010 American Institute of Physics.
Motsclés: Absolute displacement; Absorbances; AFM cantilevers; Analytical approach; Atomic force microscopes; Photothermal; Photothermal expansion; Physical assumptions; Spectromicroscopy; Theoretical investigations; Tunable infrared laser; Vibration modes; Absorption spectroscopy; Atomic force microscopy; Atomic spectroscopy; Infrared lasers; Infrared spectroscopy; Laser pulses; Photolithography; Pulsed laser applications; Resonance; Vibration analysis; Thermal expansion


Holographic laser Doppler ophthalmoscopy Simonutti, M., M. Paques, J. A. Sahel, M. Gross, B. Samson, C. Magnain, and M. Atlan Optics Letters 35, no. 12, 19411943 (2010)
Résumé: We report laser Doppler ophthalmoscopic fundus imaging in the rat eye with nearIR heterodyne holography. Sequential sampling of the beat of the reflected radiation against a frequencyshifted optical local oscillator is made onto an array detector. Widefield maps of fluctuation spectra in the 10 Hz to 25 kHz band exhibit angiographic contrasts in the retinal vascular tree without requirement of an exogenous marker. © 2010 Optical Society of America.
Motsclés: diagnostic agent; angiography; animal; animal disease; article; eye fundus; feasibility study; holography; laser; methodology; ophthalmoscopy; radiography; rat; retina; Angiography; Animals; Feasibility Studies; Fundus Oculi; Holography; Lasers; Ophthalmoscopy; Rats; Retina; Array detectors; Fluctuation spectra; Fundus imaging; Heterodyne holography; Laser doppler; Local oscillators; NearIR; Sequential sampling; Vascular trees; Widefield; Classifiers; Doppler effect; Laser recording


Semiconductor surface plasmon sources Babuty, A., A. Bousseksou, J.P. Tetienne, I. M. Doyen, C. Sirtori, G. Beaudoin, I. Sagnes, Y. De Wilde, and R. Colombelli Physical Review Letters 104, no. 22 (2010)
Résumé: Surfaceplasmon polaritons (SPPs) are propagating electromagnetic modes bound at a metaldielectric interface. We report on electrical generation of SPPs by reproducing the analogue in the near field of the slitdoublet experiment, in a device which includes all the building blocks required for a fully integrated plasmonic active source: an electrical generator of SPPs, a coupler, and a passive metallic waveguide. SPPs are generated upon injection of electrical current, and they are then launched at the edges of a passive metallic strip. The interference fringes arising from the plasmonic standing wave on the surface of the metallic strip are unambiguously detected with apertureless nearfield scanning optical microscopy. © 2010 The American Physical Society.
Motsclés: Building blockes; Electrical current; Electrical generation; Electrical generators; Electromagnetic modes; Fully integrated; Interference fringe; Metaldielectric interface; Metallic strips; Metallic waveguide; Near fields; Semiconductor surfaces; Standing wave; Surface plasmon polaritons; Near field scanning optical microscopy; Plasmons; Surface plasmon resonance; Electric generators


Chemical nanosensors based on composite molecularly imprinted polymer particles and surfaceenhanced Raman scattering Bompart, M., Y. De Wilde, and K. Haupt Advanced Materials 22, no. 21, 23432348 (2010)
Résumé: (Figure Presented) Chemical nanosensors with a submicrometer coreshell composite design, based on a polymer core, a molecularly imprinted polymer (MIP) shell for specific analyte recognition, and an interlayer of gold nanoparticles for signal amplification, are described. SERS measurements on single nanosensors yield detection limits of 107 M for the βblocker propranolol, several orders of magnitude lower than on plain MIP spheres. © 2010 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim.
Motsclés: Analytes; Coreshell composites; Detection limits; Gold Nanoparticles; Molecularly imprinted polymer; Orders of magnitude; Signal amplifications; Submicrometers; Surface enhanced Raman scattering; Amplification; Nanosensors; Raman scattering; Signal processing; Polymers; nanomaterial; polymer; propranolol; article; chemistry; conformation; crystallization; equipment; equipment design; instrumentation; macromolecule; materials testing; methodology; nanotechnology; particle size; surface plasmon r


Measurement of thickness or plate velocity using ambient vibrations Ing, R. K., N. Etaix, A. Leblanc, and M. Fink Journal of the Acoustical Society of America 127, no. 6, EL252EL257 (2010)
Résumé: Assuming the Green's function is linear with respect to the boundary conditions, it is demonstrated that flexural waves detected by a point receiver and a circular array of point receivers centered on the previous receiver are proportional regardless location of the source and geometry of the plate. Therefore determination of plate velocity or thickness is done from the measurement of ambient vibrations without using any emitter. Experimental results obtained with a plate of non regular geometry excited with a single transducer or a remote loudspeaker are shown to verify the theoretical approach. © 2010 Acoustical Society of America.
Motsclés: Ambient vibrations; Circular arrays; Flexural wave; Plate velocity; Regular geometry; Theoretical approach; Electroacoustic transducers; Thickness measurement; Green's function


Spontaneous decay rate of a dipole emitter in a strongly scattering disordered environment Pierrat, R., and R. Carminati Physical Review A  Atomic, Molecular, and Optical Physics 81, no. 6 (2010)
Résumé: We study the statistics of the fluorescence decay rate of a dipole emitter embedded in a strongly scattering medium. In the multiplescattering regime, the probability of observing a decrease in the decay rate is substantial, as predicted by exact numerical simulations. The decrease originates from a reduction of the local density of optical states and is due to collective interactions and interferences. In the strongscattering regime, signatures of recurrent scattering are visible in the behavior of the average decay rate. © 2010 The American Physical Society.
Motsclés: Decay rate; Fluorescence decays; Local density; Numerical simulation; Optical state; Scattering medium; Scattering regime; Spontaneous decay rates; Computer simulation; Decay (organic); Optical waveguides; Scattering


Photorefractive acoustooptic imaging in thick scattering media at 790 nm with a Sn2P2S6:Te crystal Farahi, S., G. Montemezzani, A. A. Grabar, J.P. Huignard, and F. Ramaz Optics Letters 35, no. 11, 17981800 (2010)
Résumé: Acoustooptic imaging is based on ultrasound modulation of multiply scattered light in thick media. We experimentally demonstrate the possibility to perform a selfadaptive wavefront holographic detection at 790 nm, within the optical therapeutic window where absorption of biological tissues is minimized. A highgain Tedoped Sn2P2S6 crystal is used for this purpose. Optical absorbing objects embedded within a thick scattering phantom are imaged by use of pulsed ultrasound to get a dynamic millimetric axial resolution. Our technique represents an interesting approach for breast cancer detection. © 2010 Optical Society of America.
Motsclés: Acoustooptic imaging; Axial resolutions; Biological tissues; Breast cancer detection; Highgain; Multiply scattered light; Photorefractive; Pulsed ultrasounds; Scattering media; Selfadaptive; Ultrasound modulation; Light scattering; Scattering; Tellurium compounds; Tin; Ultrasonics; Ultrasonic applications; article; ceramics; crystallization; elastography; equipment; equipment design; instrumentation; photometry; radiation scattering; refractometry; reproducibility; sensitivity and specificit


Resonant metalenses for breaking the diffraction barrier Lemoult, F., G. Lerosey, J. De Rosny, and M. Fink Physical Review Letters 104, no. 20 (2010)
Résumé: We introduce the resonant metalens, a cluster of coupled subwavelength resonators. Dispersion allows the conversion of subwavelength wave fields into temporal signatures while the Purcell effect permits an efficient radiation of this information in the far field. The study of an array of resonant wires using microwaves provides a physical understanding of the underlying mechanism. We experimentally demonstrate imaging and focusing from the far field with resolutions far below the diffraction limit. This concept is realizable at any frequency where subwavelength resonators can be designed. © 2010 The American Physical Society.
Motsclés: Diffraction barrier; Diffraction limits; Far field; MetaLens; Purcell effect; Subwavelength; Subwavelength resonators; Temporal signatures; Underlying mechanism; Wavefields; Resonators


Nanoparticle for active plasmonic device Delahaye, J., S. Gresillon, and E. Fort Proceedings of SPIE  The International Society for Optical Engineering 7608 (2010)
Résumé: Active plasmonic devices are much promising for optical devices and circuits at the nanoscale. We show that single nanoparticles coupled to metallic surfaces are good candidates for integrated components with nanometric dimensions. The localized plasmon of the nanoparticle launches propagating surface plasmons in the metallic thin film. Direct particle observation using leaky wave microscope geometry permits easy detection through the interference of the direct transmitted excitation light and the surface plasmon leaky mode. Investigations of the optical response of a nanoparticle deposited on metallic thin metal films reveals unexpectedly high transmission of light associated to contrast inversion in the images. © 2010 Copyright SPIE  The International Society for Optical Engineering.
Motsclés: Leaky wave; Metal particle; Microscopy; Plasmon; Polariton; Excitation light; High transmission; Leaky modes; Leaky waves; Metal particle; Metallic surface; Metallic thin films; Nano scale; Nanometric dimensions; Optical response; Plasmonpolaritons; Plasmonic devices; Single nanoparticle; Surface plasmons; Thin metal films; Light transmission; Metallic compounds; Nanoparticles; Nanophotonics; Nanotechnology; Optical data storage; Optical instruments; Phonons; Photons; Quantum theory; Plasmons


Offaxis phaseshifting holographic interferometry for the 3D localization of cellular transmembrane receptors tagged with gold nanomarkers Joud, F., N. Warnasooriya, P. Bun, G. Tessier, M. CoppeyMoisan, M. Atlan, P. Desbiolles, M. Abboud, and M. Gross Progress in Biomedical Optics and Imaging  Proceedings of SPIE 7576 (2010)
Résumé: In this communication, we show that offaxis digital holography combined to phaseshifting acquisition of holograms is an effective microscopic tool to fully localize, in three dimensions, transmembrane receptors of living cells tagged with Gold nanocolloids. Gold nanoparticles, known for their interesting optical properties as well as for their noncytotoxicity are used here as biomarkers to target the cellular receptors. © 2010 Copyright SPIE  The International Society for Optical Engineering.
Motsclés: Biomarkers; Digital holography; Gold nanoparticles; Microscopy; 3D localization; Cellular receptors; Digital holography; Gold Nanoparticles; Living cell; Microscopic tools; Nanocolloids; Offaxis; Phaseshifting; Phaseshifting holographic interferometry; Three dimensions; Transmembrane receptors; Computer generated holography; Gold; Holograms; Nanoparticles; Optical properties; Probes; Holographic interferometry


Fluorescence correlation spectroscopy on nanofakir surfaces Delahaye, J., S. Gresillon, S. LévêqueFort, N. Sojic, and E. Fort Progress in Biomedical Optics and Imaging  Proceedings of SPIE 7571 (2010)
Résumé: Single biomolecule behaviour can reveal crucial information about processes not accessible by ensemble measurements. It thus represents a real biotechnological challenge. Common optical microscopy approaches require pico to nanomolar concentrations in order to isolate an individual molecule in the observation volume. However, biologically relevant conditions often involve micromolar concentrations, which impose a drastic reduction of the conventional observation volume by at least three orders of magnitude. This confinement is also crucial for mapping subwavelength heterogeneities in cells, which play an important role in many biological processes. We propose an original approach, which couples Fluorescence Correlation Spectroscopy (FCS), a powerful tool to retrieve essential information on single molecular behaviour, and nanofakir substrates with strong field enhancements and confinements at their surface. These electromagnetic singularities at nanometer scale, called "hotspots", are the result of the unique optical properties of surface plasmons. They provide an elegant means for studying singlemolecule dynamics at high concentrations by reducing dramatically the excitation volume and enhancing the fluorophore signal by several orders of magnitude. The nanofakir substrates used are obtained from etching optical fiber bundles followed by sputtering of a gold thinfilm. It allows one to design reproducible arrays of nanotips. © 2010 Copyright SPIE  The International Society for Optical Engineering.
Motsclés: Electromagnetic enhancement; Fluorescence correlation spectroscopy; Surface plasmon; Biological process; Electromagnetic enhancement; Fluorescence Correlation Spectroscopy; High concentration; Hotspots; Incell; Micromolar concentration; Molar concentration; Nanometer scale; Optical fiber bundle; Orders of magnitude; Singlemolecule dynamics; Strong field enhancement; Subwavelength; Surface plasmons; Three orders of magnitude; Electromagnetism; Fluorescence; Fluorescence spectroscopy; Molecule


Digital holography at shot noise level Verpillat, F., F. Joud, M. Atlan, and M. Gross IEEE/OSA Journal of Display Technology 6, no. 10, 455464 (2010)
Résumé: By a proper arrangement of a digital holography setup, that combines offaxis geometry with phaseshifting recording conditions, it is possible to reach the theoretical shot noise limit, in realtime experiments. We studied this limit, and we show that it corresponds to 1 photoelectron per pixel within the whole frame sequence that is used to reconstruct the holographic image. We also show that Monte Carlo noise synthesis onto holograms measured at high illumination levels enables accurate representation of the experimental holograms measured at very weak illumination levels. An experimental validation of these results is done. © 2006 IEEE.
Motsclés: Digital holography; offaxis holography; phaseshifting; shot noise; Digital holography; Experimental validations; Frame sequences; Holographic images; Illumination levels; MONTE CARLO; Noise limit; Noise synthesis; Offaxis geometry; Offaxis holography; phaseshifting; Realtime experiment; Shotnoise level; Computer generated holography; Shot noise; Holograms


Subwavelength spatial correlations in nearfield speckle patterns Carminati, R. Physical Review A  Atomic, Molecular, and Optical Physics 81, no. 5 (2010)
Résumé: At subwavelength distance from the exit surface of a disordered medium, speckle patterns generated by multiple scattering of waves exhibit nonuniversal nearfield correlations. A calculation of the field spatial correlation function shows that the correlation length is driven by the microscopic structure of the medium. The averaged speckle spot size can be smaller than the wavelength, even for nonresonant dielectric media. © 2010 The American Physical Society.
Motsclés: Correlation lengths; Disordered medium; Microscopic structures; Nearfield; Nearfield speckles; Nonresonant dielectrics; Spatial correlation functions; Spatial correlations; Speckle patterns; Spot sizes; Subwavelength; Speckle


Separation of scales in elasticity imaging: A numerical study Ammari, H., P. Garapon, and F. Jouve Journal of Computational Mathematics 28, no. 3, 354370 (2010)
Résumé: In magnetic resonance electrograph, one seeks to reconstruct the shear modulus from measurements of the displacement field in the whole body. In this paper, we present an optimization approach which solves the problem by simply minimizing a discrepancy functional. In order to recover a complex anomaly in a homogenous medium, we first observe that the information contained in the wave field should be decomposed into two parts, a "nearfield" part in the region around the anomaly and a "farfield" part in the region away from the anomaly. As will be justified both theoretically and numerically, separating these scales provides a local and precise reconstruction. © 2010 by AMSS, Chinese Academy of Sciences.
Motsclés: Anomaly reconstruction; Elastography; Multiscale imaging


Spatiotemporal invariants of the time reversal operator Robert, J.L., and M. Fink Journal of the Acoustical Society of America 127, no. 5, 29042912 (2010)
Résumé: The decomposition of the time reversal operator, known by the French acronym DORT, is a technique to extract point scatterers monochromatic Greens functions from a medium. It is used to detect, locate, and focus on scatterers in various domains such as underwater acoustics, medical ultrasound, and nondestructive evaluation. A limitation of the method arises from its singlefrequency nature, when the signals used in acoustics are often broadband. Reconstruction of the broadband Greens functions from the singlefrequency Greens functions can be very difficult when numerous scatterers are present in the medium. Moreover, the method does not take advantage of the axial resolution associated with broadband signals. Time domain methods are investigated here as an answer to these problems. It is shown that the time reversal operator in the time domain takes the form of a tensor. The properties of the invariants are discussed. It is shown they do not have all the expected properties. Another method is proposed that requires a priori information on the medium. © 2010 Acoustical Society of America.
Motsclés: Axial resolutions; Broadband signal; Decomposition of the time reversal operator; Medical ultrasound; Non destructive evaluation; Priori information; Singlefrequency; Spatiotemporal; Time domain; Timedomain methods; Timereversal operator; Green's function; Scattering; Ultrasonic applications; Underwater acoustics; Time domain analysis; acoustics; algorithm; article; motion; radiation scattering; signal processing; sound; theoretical model; time; ultrasound; Acoustics; Algorithms; Models, The


Experimental validation of time reversal ultra wideband communication system for high data rates Naqvi, I. H., G. E. Zein, G. Lerosey, J. De Rosny, P. Besnier, A. Tourin, and M. Fink IET Microwaves, Antennas and Propagation 4, no. 5, 643650 (2010)
Résumé: An experimental validation of high data rate communication for a time reversal (TR) ultra wideband (UWB) communication system is performed using binary pulse amplitude modulation (BPAM) in two different dense multipath propagation channels for different data rates (15.62Mbps≤Rb≤1Gbps). From the measured received signals, signal, interference and noise contributions are separated. At very high data rates, interference has the most dominant contribution of all. Furthermore, without any processing and equalisation at the receiver, bit error rate (BER) performance is compared for different Rb It is shown that for Rb≤125Mbps, TR system gives a good BER performance. Finally, the authors introduce a modified TR scheme in which total bandwidth of the TR system is divided into Nsubbands contributing equal power in the power spectral density (PSD). This technique enables a flat PSD of the TR transmitted signal, reduces inter symbol interference (ISI) and therefore improves the BER performance of the system. © 2010 © The Institution of Engineering and Technology.
Motsclés: BER performance; Bit error rate performance; Data rates; Dense multipath; Dominant contributions; Equalisation; Experimental validations; High data rate; High data rate communications; Noise contributions; Propagation channels; Received signals; Time reversal; Transmitted signal; Ultrawideband communications; Amplitude modulation; Broadband networks; Communication systems; Data flow analysis; Power spectral density; Pulse amplitude modulation; Satellite communication systems; Bit error rate


Laser ultrasonic inspection of plates using zerogroup velocity lamb modes Clorennec, D., C. Prada, and D. Royer IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 57, no. 5, 11251132 (2010)
Résumé: A noncontact laserbased ultrasonic technique is proposed for detecting small plate thickness variations caused by corrosion and adhesive disbond between two plates. The method exploits the resonance at the minimum frequency of the S1 Lamb mode dispersion curve. At this minimum frequency, the group velocity vanishes, whereas the phase velocity remains finite. The energy deposited by the laser pulse generates a local resonance of the plate. This vibration is detected at the same point by an optical interferometer. First experiments show the ability to image a 1.5m deep corroded area on the back side of a 0.5mmthick duralumin plate. Because of the finite wavelength of the S1 zero group velocity (ZGV) mode, the spatial resolution is limited to approximately twice the plate thickness. With the same technique we investigate the state of adhesive bonds between duralumin and glass plates. The S 1Lamb mode resonance is strongly attenuated when plates are rigidly bonded. In the case of thin adhesive layers, we observed other resonances, associated with ZGV modes of the multilayer structure, whose frequencies and amplitudes vary with adhesive thickness. Experiments were carried out on real automotive adhesively bonded structures and the results were compared with images obtained by Xray radiography. © 2010 IEEE.
Motsclés: Adhesive bond; Adhesive layers; Adhesive thickness; Adhesively bonded structures; Disbond; Finite wavelength; Glass plate; Group velocities; Lamb modes; Laser ultrasonics; Laserbased ultrasonics; Local resonance; Multilayer structures; Noncontact; Optical interferometer; Plate thickness; Spatial resolution; Two plates; Zerogroup velocity; Light velocity; Pulsed laser applications; Resonance; Ultrasonic testing; Ultrasonics; X ray radiography; Plates (structural components)


NanoOptics: YagiUda antenna shines bright Lerosey, G. Nature Photonics 4, no. 5, 267268 (2010)


Imaging: Sharper focus by random scattering Fink, M. Nature Photonics 4, no. 5, 269271 (2010)


High intensity focused ultrasound for transcranial therapy of brain lesions and disorders Aubry, J.F., L. Marsac, M. Pernot, B. Robert, A.L. Boch, D. Chauvet, N. Salameh, L. Souris, L. Darasse, J. Bittoun, Y. Martin, C. CohenBacrie, J. Souquet, M. Fink, and M. Tanter IRBM 31, no. 2, 8791 (2010)
Résumé: A novel MRguided brain therapy device operating at 1 MHz has been designed and constructed. The system has been installed and tested in a clinical 1.5 T Philips Achieva MRI. Skull bone distortions induced on the ultrasonic beam are corrected using the concept of time reversal focusing. Prior to the treatment, a 3D CT scan of the patient head is performed and used as entry parameters for threedimensional finite differences simulations that compute the propagation of the wave field through the human skull. The simulated phase distortions are then used as inputs for transcranial corrections. Temperature elevations during the treatment are imaged using MRI thermometry thus ensuring the control and safety of this therapeutic approach. First experiments are performed on four human cadavers and the promising results allow us to envision a first clinical investigation of this therapeutic approach in a near future. First targeted applications correspond to the noninvasive treatment of brain metastases and neurologic disorders such as the essential tremor. © 2010.
Motsclés: Brain; Cancer; Focalisation; MRI; Therapy; Thermal ablation; Thermometry; Ultrasound; article; brain damage; brain disease; cadaver; computer assisted tomography; equipment design; high intensity focused ultrasound; human; image processing; image reconstruction; nuclear magnetic resonance imaging; parameter; safety; simulation; skull; thermometry; three dimensional imaging


Viscoelastic and anisotropic mechanical properties of in vivo muscle tissue assessed by supersonic shear imaging Gennisson, J.L., T. Deffieux, E. Macé, G. Montaldo, M. Fink, and M. Tanter Ultrasound in Medicine and Biology 36, no. 5, 789801 (2010)
Résumé: The in vivo assessment of the biomechanical properties of the skeletal muscle is a complex issue because the muscle is an anisotropic, viscoelastic and dynamic medium. In this article, these mechanical properties are characterized for the brachialis muscle in vivo using a noninvasive ultrasoundbased technique. This supersonic shear imaging technique combines an ultrafast ultrasonic system and the remote generation of transient mechanical forces into tissue via the radiation force of focused ultrasonic beams. Such an ultrasonic radiation force is induced deep within the muscle by a conventional ultrasonic probe and the resulting shear waves are then imaged with the same probe (5 MHz) at an ultrafast framerate (up to 5000 frames/s). Local tissue velocity maps are obtained with a conventional speckle tracking technique and provide a full movie of the shear wave propagation through the entire muscle. Shear wave group velocities are then estimated using a time of flight algorithm. This approach provides a complete set of quantitative and in vivo parameters describing the muscle's mechanical properties as a function of active voluntary contraction as well as passive extension of healthy volunteers. Anisotropic properties are also estimated by tilting the probe head with respects to the main muscular fibers direction. Finally, the dispersion of the shear waves is studied for these different configurations and shear modulus and shear viscosity are quantitatively assessed assuming the viscoelastic Voigt's model. © 2010 World Federation for Ultrasound in Medicine & Biology.
Motsclés: Anisotropy; Muscle tissue; Supersonic shear imaging; Transient elastography; Viscoelastic; Anisotropic mechanical properties; Anisotropic property; Biomechanical properties; Framerate; Invivo; Muscle tissues; Radiation forces; Shear modulus; Skeletal muscle; Speckle tracking technique; Supersonic shear imaging; Time of flight; Transient elastography; Transient mechanical; Ultrafast; Ultrasonic beams; Ultrasonic probe; Ultrasonic radiation force; Ultrasonic system; Velocity maps; Voluntary con


Diffusionweighted MR imaging of the liver Vilgrain, V., J.L. Daire, R. Sinkus, and B. E. Van Beers Journal de Radiologie 91, no. 3 C2, 381393 (2010)
Résumé: Diffusionweighted MR imaging of the liverDiffusionweighted imaging studies the motion of water molecules within a given tissue. Initially used for neuroradiological applications, it is now routinely used for abdominal imaging, especially liver imaging. The diffusion pulse sequence is a T2 echoplanar sequence where diffusion gradients are applied. In this article, we will review the sequence itself and the parameters used to optimize the sequence, quantitative and qualitative image evaluation, and the main applications for liver imaging: characterization of focal lesions, detection of focal lesions, evaluation of response to therapy and quantification of liver fibrosis. © 2010. Éditions Françaises de Radiologie.
Motsclés: Functional MRI fibrosis; Functional MRI tumors; Liver fibrosis; Liver imaging techniques; Liver tumors; article; diffusion weighted imaging; echo planar imaging; human; image analysis; liver cell carcinoma; liver disease; liver fibrosis; liver metastasis; qualitative analysis; quantitative analysis; treatment response; Diffusion Magnetic Resonance Imaging; EchoPlanar Imaging; Humans; Image Enhancement; Liver Cirrhosis; Liver Diseases; Liver Neoplasms; Prognosis


Asymptotic imaging of perfectly conducting cracks Ammarl, H., H. Rang, H. Lee, and W.K. Park SIAM Journal on Scientific Computing 32, no. 2, 894922 (2010)
Résumé: In this paper, we consider cracks with Dirichlet boundary conditions. We first derive an asymptotic expansion of the boundary perturbations that are due to the presence of a small crack. Based on this formula, we design a noniterative approach for loc ating a collection of small cracks. In order to do so, we construct a response matrix from the boundary measurements. The location and the length of the crack are estimated, respectively, from the pro jection onto the noise space and the first significant singular value of the response matrix. Indeed, the direction of the crack is estimated from the second singular vector. We then consider an extended crack with Dirichlet boundary conditions. We rigorously derive an asymptotic expansion for t he boundary perturbations that are due to a shape deformation of the crack. To reconstruct an extended crack from many boundary measurements, we develop two methods for obtaining a good guess. Several numerical experiments show how the proposed techniques for imaging small cracks as well as those for obtaining good initial guesses toward reconstructing an extended crack behave. © 2010 Society for Industrial and Applied Mathematics.
Motsclés: Asymptotic imaging; Crack detection; Reconstruction algorithm; Asymptotic expansion; Boundary measurements; Boundary perturbations; Conducting crack; Dirichlet boundary condition; Initial guess; Noise spaces; Noniterative; Numerical experiments; Reconstruction algorithms; Response matrices; Shape deformation; Singular values; Singular vectors; Small crack; Asymptotic analysis; Boundary conditions; Crack detection


Frequencyresolved temperature imaging of integrated circuits with full field heterodyne interferometry Suck, S. Y., G. Tessier, N. Warnasooriya, A. Babuty, and Y. De Wilde Applied Physics Letters 96, no. 12 (2010)
Résumé: We report a fast imaging method based on full field heterodyne interferometry for the purpose of frequency resolved temperature imaging. An integrated circuit is supplied with a modulated current resulting into a temperature modulation. The frequency content for this modulation is detected using an object beam and a reference beam, frequencyshifted to create a beating of the interference pattern. We obtain frequency domain spectra of the temperature with excellent precision. © 2010 American Institute of Physics.
Motsclés: Fast imaging; Frequency contents; Frequency domains; Fullfield; Heterodyne interferometry; Interference patterns; Modulated current; Object beam; Reference beams; Temperature imaging; Temperature modulation; Heterodyning; Integrated circuits; Interferometry; Light measurement


Experimental study of the invariants of the timereversal operator for a dielectric cylinder using separate transmit and receive arrays Davy, M., J.G. Minonzio, J. De Rosny, C. Prada, and M. Fink IEEE Transactions on Antennas and Propagation 58, no. 4, 13491356 (2010)
Résumé: The decomposition of the time reversal operator (DORT method) is applied to electromagnetic waves in order to characterize a dielectric cylinder. It consists in determining the Time Reversal Invariants of the Time Reversal Operator. Here, this matrix is built from the interelement responses between distinct transmit and receive arrays. In this paper experimental results obtained between 2 and 4 GHz are compared to a theoretical model, developed in an other paper (Minonzio , Theory of the timereversal operator for a dielectric cylinder using separate transmit and receive arrays, IEEE Trans. Antennas Propag., vol. 57, pp. 23312340, 2009). The DORT method is then applied to an inverse problem to determine the diameter and the permittivity of the cylinder. It is shown experimentally that different experimental parameters can be estimated from the singular values of the time reversal operator. © 2006 IEEE.
Motsclés: Antenna array processing; Electromagnetic inverse problem; Electromagnetic scattering; Decomposition of the time reversal operator; Dielectric cylinder; Electromagnetic inverse problems; Electromagnetic scattering; Experimental parameters; Experimental studies; matrix; Singular values; Theoretical models; Time reversal; Timereversal operator; Antenna arrays; Array processing; Cylinders (shapes); Dielectric devices; Electromagnetic wave scattering; Electromagnetic waves; Inverse problems; Microw


Non invasive transcostal focusing based on the decomposition of the time reversal operator: In vitro validation Cochard, É., C. Prada, J.F. Aubry, and M. Fink AIP Conference Proceedings 1215, 131135 (2010)
Résumé: Thermal ablation induced by high intensity focused ultrasound has produced promising clinical results to treat hepatocarcinoma and other liver tumors. However skin burns have been reported due to the high absorption of ultrasonic energy by the ribs. This study proposes a method to produce an acoustic field focusing on a chosen target while sparing the ribs, using the decomposition of the timereversal operator (DORT method). The idea is to apply an excitation weight vector to the transducers array which is orthogonal to the subspace of emissions focusing on the ribs. The ratio of the energies absorbed at the focal point and on the ribs has been enhanced up to 100fold as demonstrated by the measured specific absorption rates. © 2010 American Institute of Physics.
Motsclés: Adaptive focusing; DORT; High intensity focused ultrasound; Noninvasive surgery; Phased array


MRguided ultrasonic brain therapy: High frequency approach Aubry, J. F., L. Marsac, M. Pernot, M. Tanter, B. Robert, M. Brentnall, P. Annic, R. La Greca, A. De Charentenay, F. Pomatta, Y. Martin, C. CohenBacrie, J. Souquet, and M. Fink AIP Conference Proceedings 1215, 8894 (2010)
Résumé: A novel MRguided brain therapy device operating at 1 MHz has been designed and constructed. The system has been installed and tested in a clinical 1.5 T Philips Achieva MRI. Three dimensional time domain finite differences simulations were used to compute the propagation of the wave field through three human skulls. The simulated phase distortions were used as inputs for transcranial correction and the corresponding pressure fields were scanned in the focal plane. At half of the maximum power (10W/cm2 on the surface of the transducers), necroses were induced 2 cm deep in turkey breasts placed behind a human skull. In vitro experiments on human skulls show that simulations restore more than 85% of the pressure level through the skull bone when compared to a control correction performed with an implanted hydrophone. Finally, high power experiments are performed though the skull bone and a MRThermometry sequence is used to map the temperature rise in a brain phantom every 3 s in two orthogonal planes (focal plane and along the axis of the probe). © 2010 American Institute of Physics.
Motsclés: HIFU; MR guided therapy; Transcranial therapy


MR guidance, monitoring and control of brain HIFU therapy in small animals: In vivo demonstration in rats Larrat, B., M. Pernot, E. Dervishi, A. Souilah, D. Seilhean, Y. Marie, A. L. Boch, J. F. Aubry, M. Fink, and M. Tanter AIP Conference Proceedings 1215, 105109 (2010)
Résumé: In the framework of HIFU transcranial brain therapy, it is mandatory to develop techniques capable of assessing the focusing quality and location before the treatment. Monitoring heat deposition in real time and verifying the extension of the treated area are also important steps. In this study, an imaging protocol is proposed to:1/ locate the US radiation force induced displacement in tissues and quantify the acoustic pressure at focus prior to HIFU; 2/ monitor the temperature rise during HIFU; and 3/ assess the changes in elasticity in the treated area. A 7T MRI scanner was equipped with a homemade stereotactic frame for rats and a US focused transducer working at 1.5 MHz. Such a tool is key for the evaluation of the biological effects of HIFU on brain tissue and tumors. The proposed protocol was successfully tested on 12 rats with and without injected tumors. The accurate localization of the focal point prior to HIFU was demonstrated in vivo. Furthermore, the pressure estimation in situ allowed to accurately simulate the heat deposition at focus and to plan the treatment (electrical power, duration). The temperature measurements were in good accordance with the predicted curves. The elasticity maps showed significant changes after treatment in some cases. © 2010 American Institute of Physics.
Motsclés: Brain; High intensity focused ultrasound; Magnetic resonance elastography; Magnetic resonance thermometry; Monitoring; Radiation force localization; Rat; Transcranial


Energybased adaptive focusing: Optimal ultrasonic focusing using magnetic resonance guidance Larrat, B., M. Pernot, G. Montaldo, M. Fink, and M. Tanter AIP Conference Proceedings 1215, 140144 (2010)
Résumé: Adaptive focusing of ultrasonic waves is performed under the guidance of a Magnetic Resonance (MR) system. The technique is based on the maximization of the ultrasonic wave intensity at a target point. The wave intensity is indirectly estimated from the local tissue motion induced at the chosen focus by the acoustic radiation force of the ultrasonic beam. A motion sensitive MR sequence is used to measure the resulting local tissue displacements. Based on the transmission of a set of spatially coded ultrasonic waves, a non iterative inversion process is used to estimate the phase aberrations induced by the propagation medium and to maximize the acoustical intensity at the target. Both programmable and physical aberrating layers introducing strong distortions (up to 2π radians) are recovered within acceptable errors (<0.8 rad). This non invasive technique is shown to accurately correct the phase aberrations in a phantom gel with negligible heat deposition and limited acquisition time. These refocusing performances demonstrate a major potential in the field of MRGuided Ultrasound Therapy in particular for transcranial brain HIFU. © 2010 American Institute of Physics.
Motsclés: Acoustic radiation force; Adaptive focusing; HIFU; MR guided therapy; Transcranial therapy


Transient thermoreflectance imaging of active photonic crystals Moreau, V., G. Tessier, F. Raineri, M. Brunstein, A. Yacomotti, R. Raj, I. Sagnes, A. Levenson, and Y. De Wilde Applied Physics Letters 96, no. 9 (2010)
Résumé: Transient thermoreflectance imaging is used to study the dynamics of the temperature inside active twodimensional photonic crystals (PhCs). We developed a pumpprobe setup suited for optically pumped devices that presents submicrosecond time resolution and submicrometer spatial resolution. Characteristic thermal dissipation times of 429 ns in a PhC Bloch mode cavity and of 999 ns in a PhC membrane are measured. This technique gives also access to the diffusivity of the suspended PhC. © 2010 American Institute of Physics.
Motsclés: Active photonic crystals; Bloch modes; Diffusivities; Optically pumped; Pumpprobe; Spatial resolution; Submicrosecond; Submicrometers; Thermal dissipation; Time resolution; Transient thermoreflectance; Twodimensional photonic crystals; Photonic crystals


Tunable trapped mode in symmetric resonator designed for metamaterials Ourir, A., R. Abdeddaim, and J. De Rosny Progress in Electromagnetics Research 101, 115123 (2010)
Résumé: The excitation of an antisymmetric trapped mode on a symmetric metamaterial resonator is experimentally demonstrated. We use an active electronic device to break the electrical symmetry and therefore to generate this trapped mode on a symmetric spilt ring resonator. Even more, with such a tunable mode coupling resonator, we can precisely tune the resonant mode frequency. In this way, a shift of up to 15 percent is observed.
Motsclés: Active electronic devices; Antisymmetric; Mode coupling; Resonant mode; Ring resonator; Trapped modes; Electronic equipment; Metamaterials; Resonators


Compressed sensing with offaxis frequencyshifting holography Marim, M. M., M. Atlan, E. Angelini, and J.C. OlivoMarin Optics Letters 35, no. 6, 871873 (2010)
Résumé: This work reveals an experimental microscopy acquisition scheme successfully combining compressed sensing (CS) and digital holography in offaxis and frequencyshifting conditions. CS is a recent data acquisition theory involving signal reconstruction from randomly undersampled measurements, exploiting the fact that most images present some compact structure and redundancy. We propose a genuine CSbased imaging scheme for sparse gradient images, acquiring a diffraction map of the optical field with holographic microscopy and recovering the signal from as little as 7% of random measurements. We report experimental results demonstrating how CS can lead to an elegant and effective way to reconstruct images, opening the door for new microscopy applications. © 2010 Optical Society of America.
Motsclés: Compact structures; Compressed sensing; Digital holography; Frequencyshifting; Gradient images; Holographic microscopy; Imaging schemes; Offaxis; Optical field; Random measurement; Computer generated holography; Signal reconstruction; Signal processing; algorithm; article; holography; image processing; light related phenomena; methodology; Algorithms; Holography; Image Processing, ComputerAssisted; Optical Processes


NanoOptics: YagiUda antenna shines bright Lerosey, G. Nature Photonics (2010)


Temperature dependence of the shear modulus of soft tissues assessed by ultrasound SapinDe Brosses, E., J.L. Gennisson, M. Pernot, M. Fink, and M. Tanter Physics in Medicine and Biology 55, no. 6, 17011718 (2010)
Résumé: Soft tissue stiffness was shown to significantly change after thermal ablation. To better understand this phenomenon, the study aims (1) to quantify and explain the temperature dependence of soft tissue stiffness for different organs, (2) to investigate the potential relationship between stiffness changes and thermal dose and (3) to study the reversibility or irreversibility of stiffness changes. Ex vivo bovine liver and muscle samples (N = 3 and N = 20, respectively) were slowly heated and cooled down into a thermally controlled saline bath. Temperatures were assessed by thermocouples. Sample stiffness (shear modulus) was provided by the quantitative supersonic shear imaging technique. Changes in liver stiffness are observed only after 45 °C. In contrast, between 25 °C and 65 °C, muscle stiffness varies in four successive steps that are consistent with the thermally induced proteins denaturation reported in the literature. After a 6 h long heating and cooling process, the final muscle stiffness can be either smaller or bigger than the initial one, depending on the stiffness at the end of the heating. Another important result is that stiffness changes are linked to thermal dose. Given the high sensitivity of ultrasound to protein denaturation, this study gives promising prospects for the development of ultrasoundguided HIFU systems. © 2010 Institute of Physics and Engineering in Medicine.
Motsclés: Bovine liver; Cooling process; Exvivo; High sensitivity; Liver stiffness; Muscle stiffness; Protein denaturation; Shear modulus; Soft tissue; Supersonic shear imaging; Temperature dependence; Thermal ablation; Thermal dose; Thermally induced; Coagulation; Elastic moduli; Heating; Imaging techniques; Liver; Muscle; Proteins; Temperature distribution; Thermocouples; Ultrasonic applications; Ultrasonics; Stiffness


Measuring the transmission matrix in optics: An approach to the study and control of light propagation in disordered media Popoff, S. M., G. Lerosey, R. Carminati, M. Fink, A. C. Boccara, and S. Gigan Physical Review Letters 104, no. 10 (2010)
Résumé: We introduce a method to experimentally measure the monochromatic transmission matrix of a complex medium in optics. This method is based on a spatial phase modulator together with a fullfield interferometric measurement on a camera. We determine the transmission matrix of a thick random scattering sample. We show that this matrix exhibits statistical properties in good agreement with random matrix theory and allows light focusing and imaging through the random medium. This method might give important insight into the mesoscopic properties of a complex medium. © 2010 The American Physical Society.
Motsclés: Complex medium; Disordered media; Fullfield; Interferometric measurement; matrix; Mesoscopic properties; Random matrix theory; Random medium; Random scattering; Spatial phase modulator; Statistical properties; Transmission matrix; Light; Light propagation; Light transmission


Parallel heterodyne detection of dynamic lightscattering spectra from gold nanoparticles diffusing in viscous fluids Atlan, M., P. Desbiolles, M. Gross, and M. CoppeyMoisan Optics Letters 35, no. 5, 787789 (2010)
Résumé: We developed a microscope intended to probe, using a parallel heterodyne receiver, the fluctuation spectrum of light quasielastically scattered by gold nanoparticles diffusing in viscous fluids. The cutoff frequencies of the recorded spectra scale up linearly with those expected from singlescattering formalism in a wide range of dynamic viscosities (1 to 15 times water viscosity at room temperature). Our scheme enables ensembleaveraged optical fluctuations measurements over multispeckle recordings in low light, at temporal frequencies up to 10 kHz, with a 12 Hz framerate array detector. © 2010 Optical Society of America.
Motsclés: Array detectors; Dynamic viscosities; Fluctuation spectra; Framerate; Gold Nanoparticles; Heterodyne receivers; Low light; Optical fluctuation; Parallel heterodyne detection; Room temperature; Scaleup; Single scattering; Temporal frequency; Viscous fluids; Water viscosity; Cutoff frequency; Nanoparticles; Viscosity; Viscous flow; Heterodyning; gold; nanoparticle; article; chemistry; equipment; equipment design; instrumentation; light; microscopy; photometry; radiation scattering; Raman spectro


Editorial for the special issue on signal models and representations of musical and environmental sounds David, B., M. Goto, L. Daudet, and P. Smaragdis IEEE Transactions on Audio, Speech and Language Processing 18, no. 3, 417419 (2010)


Controlling the quantum yield of a dipole emitter with coupled plasmonic modes Vandenbem, C., D. Brayer, L. S. FroufePérez, and R. Carminati Physical Review B  Condensed Matter and Materials Physics 81, no. 8 (2010)
Résumé: We study theoretically the possibility of controlling the quantum yield of a single dipole emitter using coupled plasmonic modes. Plasmon hybridization offers spectral and spatial degrees of freedom that can be used to tune the spontaneous decay rate and the apparent quantum yield with high sensitivity. We demonstrate this concept on simple structures that could be implemented experimentally. © 2010 The American Physical Society.


Nonlinear reflection of shock shear waves in soft elastic media Pinton, G., F. Coulouvrat, J.L. Gennisson, and M. Tanter Journal of the Acoustical Society of America 127, no. 2, 683691 (2010)
Résumé: For fluids, the theoretical investigation of shock wave reflection has a good agreement with experiments when the incident shock Mach number is large. But when it is small, theory predicts that Mach reflections are physically unrealistic, which contradicts experimental evidence. This von Neumann paradox is investigated for shear shock waves in soft elastic solids with theory and simulations. The nonlinear elastic wave equation is approximated by a paraxial wave equation with a cubic nonlinear term. This equation is solved numerically with finite differences and the Godunov scheme. Three reflection regimes are observed. Theory is developed for shock propagation by applying the RankineHugoniot relations and entropic constraints. A characteristic parameter relating diffraction and nonlinearity is introduced and its theoretical values are shown to match numerical observations. The numerical solution is then applied to von Neumann reflection, where curved reflected and Mach shocks are observed. Finally, the case of weak von Neumann reflection, where there is no reflected shock, is examined. The smooth but nonmonotonic transition between these three reflection regimes, from linear SnellDescartes to perfect grazing case, provides a solution to the acoustical von Neumann paradox for the shear wave equation. This transition is similar to the quadratic nonlinearity in fluids. © 2010 Acoustical Society of America.
Motsclés: Characteristic parameter; Descartes; Elastic media; Elastic solids; Experimental evidence; Finite difference; Godunov scheme; Incident shock; Mach reflection; NonLinearity; Nonlinear elastic wave equations; Nonlinear terms; Numerical solution; Paraxial wave equation; RankineHugoniot relations; Reflected shocks; Shock propagation; Shock wave reflection; Theoretical investigations; Theoretical values; Von Neumann paradox; Von Neumann reflection; Linearization; Mach number; Nonlinear equations; N


Radiative corrections to the polarizability tensor of an electrically small anisotropic dielectric particle Albaladejo, S., R. GómezMedina, L. S. FroufePérez, H. Marinchio, R. Carminati, J. F. Torrado, G. Armelles, A. GarcíaMartín, and J. J. Sáenz Optics Express 18, no. 4, 35563567 (2010)
Résumé: Radiative corrections to the polarizability tensor of isotropic particles are fundamental to understand the energy balance between absorption and scattering processes. Equivalent radiative corrections for anisotropic particles are not well known. Assuming that the polarization within the particle is uniform, we derived a closedform expression for the polarizability tensor which includes radiative corrections. In the absence of absorption, this expression of the polarizability tensor is consistent with the optical theorem. An analogous result for infinitely long cylinders was also derived. Magneto optical Kerr effects in nonabsorbing nanoparticles with magnetooptical activity arise as a consequence of radiative corrections to the electrostatic polarizability tensor. © 2010 Optical Society of America.
Motsclés: Anisotropic dielectrics; Anisotropic particles; Closedform expression; Isotropic particles; Magnetooptical activity; Magnetooptical Kerr effects; Optical theorem; Polarizability tensor; Radiative corrections; Scattering process; Absorption; Anisotropy; Gene expression; High energy physics; Kerr magnetooptical effect; Magnetic field effects; Magnetos; Tensors; Optical Kerr effect; anisotropy; article; computer simulation; electromagnetic field; impedance; particle size; radiation dose; radiati


Imaging gold nanoparticles in living cell environments using heterodyne digital holographic microscopy Warnasooriya, N., F. Joud, P. Bun, G. Tessier, M. CoppeyMoisan, P. Desbiolles, M. Atlan, M. Abboud, and M. Gross Optics Express 18, no. 4, 32643273 (2010)
Résumé: This paper describes an imaging microscopic technique based on heterodyne digital holography where subwavelengthsized gold colloids can be imaged in cell environments. Surface cellular receptors of 3T3 mouse fibroblasts are labeled with 40 nm gold nanoparticles, and the biological specimen is imaged in a total internal reflection configuration with holographic microscopy. Due to a higher scattering efficiency of the gold nanoparticles versus that of cellular structures, accurate localization of a gold marker is obtained within a 3D mapping of the entire sample's scattered field, with a lateral precision of 5 mn and 100 nm in the x,y and in the z directions respectively, demonstrating the ability of holographic microscopy to locate nanoparticles in living cell environments. © 2010 Optical Society of America.
Motsclés: 3D mapping; Biological specimens; Cellular receptors; Cellular structure; Digital holographic microscopy; Digital holography; Gold colloid; Gold Nanoparticles; Holographic microscopy; Incell; Living cell; Microscopic techniques; Mousefibroblasts; Scattered field; Scattering efficiency; Subwavelength; Total internal reflections; Zdirections; Cell culture; Computer generated holography; Heterodyning; Nanoparticles; Refractive index; Three dimensional; Gold; gold; nanoparticle; animal; article


Multiwave imaging and super resolution Fink, M., and M. Tanter Physics Today 63, no. 2, 2833 (2010)
Résumé: The human body supports the propagation of many kinds of waves, each of which can provide an image with a specific type of information. For example, ultrasonic waves reveal a tissue's density and how it responds to compression forces, and mechanical shear waves indicate how tissues respond to shear forces. Lowfrequency electromagnetic waves are sensitive to electrical conductivity; optical waves tell about optical absorption. In all those circumstances, physicists have striven to obtain the best overall contrast and resolution. Now, after decades of work, we are pushing against the physical limits inherent in each imaging modality. As described in the box on page 30, that limit is, in many cases, not determined by wavelength. © 2010 American Institute of Physics.


Excitation and focusing of Lamb waves in a multilayered anisotropic plate Chapuis, B., N. Terrien, and D. Royer Journal of the Acoustical Society of America 127, no. 1, 198203 (2010)
Résumé: The radiation of Lamb waves by an axisymmetric source on the surface of an anisotropic plate is investigated. An analytical expression of the Green's function, valid in the far field domain, is derived. This approximation shows that the anisotropy of the propagation medium induces a focusing of Lamb modes in some directions, which correspond to minima of the slowness. Numerical simulations and experiments demonstrate that for the fundamental A 0 and S 0 modes, this phenomenon, analog to the phonon focusing effect, can be very strong in materials such as composite fiberreinforced polymers. This effect due to the plate anisotropy must be correctly taken into account, for example, in order to develop systems for in situ structural health monitoring. The choice of the most appropriate Lamb mode, the excitation frequency, and the design of the array of piezoelectric disks used as transmitters and receivers depends on such considerations. © 2010 Acoustical Society of America.
Motsclés: Analytical expressions; Anisotropic plates; Axisymmetric; Composite fibers; Excitation frequency; Far field; Insitu; Lamb modes; Lamb Wave; Multilayered; Numerical simulation; Phonon focusing; Piezoelectric disks; Computer simulation; Fiber reinforced materials; Gene expression; Green's function; Plates (structural components); Structural health monitoring; Ultrasonic waves; Anisotropy; acoustics; algorithm; anisotropy; article; computer simulation; electronics; methodology; theoretical model;


A unifying fractional wave equation for compressional and shear waves Holm, S., and R. Sinkus Journal of the Acoustical Society of America 127, no. 1, 542548 (2010)
Résumé: This study has been motivated by the observed difference in the range of the powerlaw attenuation exponent for compressional and shear waves. Usually compressional attenuation increases with frequency to a power between 1 and 2, while shear wave attenuation often is described with powers less than 1. Another motivation is the apparent lack of partial differential equations with desirable properties such as causality that describe such wave propagation. Starting with a constitutive equation which is a generalized Hooke's law with a loss term containing a fractional derivative, one can derive a causal fractional wave equation previously given by Caputo [Geophys J. R. Astron. Soc. 13, 529539 (1967)] and Wismer [J. Acoust. Soc. Am. 120, 34933502 (2006)]. In the low ω τ (lowfrequency) case, this equation has an attenuation with a powerlaw in the range from 1 to 2. This is consistent with, e.g., attenuation in tissue. In the often neglected high ω τ (highfrequency) case, it describes attenuation with a powerlaw between 0 and 1, consistent with what is observed in, e.g., dynamic elastography. Thus a unifying wave equation derived properly from constitutive equations can describe both cases. © 2010 Acoustical Society of America.
Motsclés: Compressional; Compressional attenuation; Elastography; Fractional derivatives; Fractional wave equation; High frequency HF; Hooke's Law; Low frequency; Powerlaw; Shear wave attenuation; Constitutive equations; Differential equations; Programmable logic controllers; Shear flow; Shear waves; Wave equations; polyethylene; viscoelastic substance; acoustics; algorithm; article; brain; breast; chemistry; flow kinetics; human; liver; mechanical stress; mechanics; methodology; physiology; pressure; st


Towards a random laser with cold atoms Guerin, W., N. Mercadier, F. Michaud, D. Brivio, L. S. FroufePérez, R. Carminati, V. Eremeev, A. Goetschy, S. E. Skipetrov, and R. Kaiser Journal of Optics A: Pure and Applied Optics 12, no. 2 (2010)
Résumé: Atoms can scatter light and they can also amplify it by stimulated emission. From this simple starting point, we examine the possibility of realizing a random laser in a cloud of lasercooled atoms. The answer is not obvious as both processes (elastic scattering and stimulated emission) seem to exclude one another: pumping atoms to make them behave as an amplifier drastically reduces their scattering crosssection. However, we show that even the simplest atom model allows the efficient combination of gain and scattering. Moreover, the supplementary degrees of freedom that atoms offer allow the use of several gain mechanisms, depending on the pumping scheme. We thus first study these different gain mechanisms and show experimentally that they can induce (standard) lasing. We then present how the constraint of combining scattering and gain can be quantified, which leads to an evaluation of the random laser threshold. The results are promising and we draw some prospects for a practical realization of a random laser with cold atoms. © 2010 IOP Publishing Ltd.
Motsclés: Cold atoms; Random laser; Cold atoms; Degrees of freedom; Lasercooled atoms; Practical realizations; Pumping schemes; Random lasers; Scattering cross section; Degrees of freedom (mechanics); Laser beams; Pumps; Scattering; Stimulated emission; Atoms


Diagnostic value of MR elastography in addition to contrastenhanced MR imaging of the breast  Initial clinical results Siegmann, K. C., T. Xydeas, R. Sinkus, B. Kraemer, U. Vogel, and C. D. Claussen European Radiology 20, no. 2, 318325 (2010)
Résumé: Objective: The purpose of the study was to assess the additional value of magnetic resonance (MR) elastography (MRE) to contrastenhanced (ce) MR imaging (MRI) for breast lesion characterisation. Methods: Fiftyseven suspected breast lesions in 57 patients (mean age 52.4 years) were examined by ce MRI and MRE. All lesions were classified into BIRADS categories. Viscoelastic parameters, e.g. α0 as an indicator of tissue stiffness, were calculated. Histology of the lesions was correlated with BIRADS and viscoelastic properties. The positive predictive value (PPV) for malignancy, and the sensitivity and specificity of ce MRI were calculated. Receiveroperating characteristics (ROC) curves were separately calculated for both ce MRI and viscoelastic properties and conjoined to analyse the accuracy of diagnostic performance. Results: The lesions (mean size 27.6 mm) were malignant in 64.9% (n=37) of cases. The PPV for malignancy was significantly (p< 0.0001) dependent on BIRADS classification. The sensitivity of ce MRI for breast cancer detection was 97.3% (36/37), whereas specificity was 55% (11/20). If ce MRI was combined with α0, the diagnostic accuracy could be significantly increased (p<0.05; AUCceMRI=0.93, AUCcombined=0.96). Conclusions: In this study, the combination of MRE and ce MRI could increase the diagnostic performance of breast MRI. Further investigations of larger cohorts and smaller lesions (in particular those only visible on MRI) are necessary to validate these results. © European Society of Radiology 2009.
Motsclés: Breast; Diagnostic value; MR elastography; MRE; MRI; adult; article; breast cancer; breast lesion; clinical protocol; clinical trial; contrast enhancement; diagnostic accuracy; diagnostic value; disease classification; female; human; human tissue; magnetic resonance elastography; major clinical study; nuclear magnetic resonance imaging; prediction; priority journal; receiver operating characteristic; sensitivity and specificity; tissue structure; viscoelasticity; breast tumor; elastography; imag


Fluorescence quenching by a metal nanoparticle in the extreme nearfield regime Castanié, E., M. Boffety, and R. Carminati Optics Letters 35, no. 3, 291293 (2010)
Résumé: We study the spontaneous decay rate of a dipóle emitter close to a metallic nanoparticle in the extreme nearfield regime. The metal is modeled using a nonlocal dielectric function that accounts for the microscopic length scales of the free electron gas. We describe quantitatively the crossover between the macroscopic and microscopic regimes and the enhanced nonradiative decay due to microscopic interactions. Our theory is in agreement with results previously established in the asymptotic near and farfield regimes. © 2010 Optical Society of America.
Motsclés: Dielectric functions; Farfield; Fluorescence quenching; Free electron gas; Metal nanoparticles; Metallic nanoparticles; Microscopic interaction; Microscopic length scale; Nearfield; Nonlocal; Nonradiative decays; Spontaneous decay rates; Decay (organic); Electron gas; Nanoparticles


Surface acoustic waves in interaction with a dislocation Maurel, A., V. Pagneux, F. Barra, and F. Lund Ultrasonics 50, no. 2, 161166 (2010)
Résumé: A surface acoustic wave can interact with dislocations that are close to the surface. We characterize this interaction and its manifestations as scattered surface acoustic waves for different orientations with respect to the surface of an edge dislocation. For dislocations that are parallel or perpendicular to the free surface, we present an analytical result for short dislocations with respect to the wavelength that reproduce qualitatively the main features observed for dislocations of various sizes. © 2009 Elsevier B.V. All rights reserved.
Motsclés: Dislocations; Scattering; Surface acoustic waves; Analytical results; Edge dislocation; Free surfaces; Scattering surface; Surface acoustic waves; Acoustic surface wave devices; Acoustic waves; Acoustics; Acoustoelectric effects; Acoustic wave scattering


MRguided transcranial brain HIFU in small animal models Larrat, B., M. Pernot, J.F. Aubry, E. Dervishi, R. Sinkus, D. Seilhean, Y. Marie, A.L. Boch, M. Fink, and M. Tanter Physics in Medicine and Biology 55, no. 2, 365388 (2010)
Résumé: Recent studies have demonstrated the feasibility of transcranial highintensity focused ultrasound (HIFU) therapy in the brain using adaptive focusing techniques. However, the complexity of the procedures imposes provision of accurate targeting, monitoring and control of this emerging therapeutic modality in order to ensure the safety of the treatment and avoid potential damaging effects of ultrasound on healthy tissues. For these purposes, a complete workflow and setup for HIFU treatment under magnetic resonance (MR) guidance is proposed and implemented in rats. For the first time, tissue displacements induced by the acoustic radiation force are detected in vivo in brain tissues and measured quantitatively using motionsensitive MR sequences. Such a valuable target control prior to treatment assesses the quality of the focusing pattern in situ and enables us to estimate the acoustic intensity at focus. This MRacoustic radiation force imaging is then correlated with conventional MRthermometry sequences which are used to follow the temperature changes during the HIFU therapeutic session. Last, pre and posttreatment magnetic resonance elastography (MRE) datasets are acquired and evaluated as a new potential way to noninvasively control the stiffness changes due to the presence of thermal necrosis. As a proof of concept, MRguided HIFU is performed in vitro in turkey breast samples and in vivo in transcranial rat brain experiments. The experiments are conducted using a dedicated MRcompatible HIFU setup in a highfield MRI scanner (7 T). Results obtained on rats confirmed that both the MR localization of the US focal point and the pre and postHIFU measurement of the tissue stiffness, together with temperature control during HIFU are feasible and valuable techniques for efficient monitoring of HIFU in the brain. Brain elasticity appears to be more sensitive to the presence of oedema than to tissue necrosis. © 2010 Institute of Physics and Engineering in Medicine.
Motsclés: Acoustic radiation force; Adaptive focusing; Brain tissue; Damaging effects; Data sets; Efficient monitoring; Focal points; Healthy tissues; High field MRI; High intensity focused ultrasound; Insitu; Invitro; Invivo; Magnetic resonance elastography; Magnetic resonance guidances; Monitoring and control; MR sequence; MRcompatible; MRthermometry; Post treatment; Proof of concept; Rat brain; Small animal model; Temperature changes; Therapeutic modality; Thermal necrosis; Tissue displacement; Ti


Photothermal heterodyne holography of gold nanoparticles Absil, E., G. Tessier, M. Gross, M. Atlan, N. Warnasooriya, S. Suck, M. CoppeyMoisan, and D. Fournier Optics Express 18, no. 2, 780786 (2010)
Résumé: We report a method based on heterodyne numerical holography associated to photothermal excitation for full field and threedimensional localisation of metallic nanoparticles. A modulated pump laser (γ = 532 nm) heats several particles, creating local refractive index changes. This modulation is detected using a probe and a local oscillator beam (γ = 785 nm), frequencyshifted to create a hologram beating at low frequency. Tens of particles, down to diameters of 10 nm, can be localised simultaneously and selectively in three dimensions with near diffraction resolution by a numerical reconstruction of a single hologram acquired in 5 s. © 2009 Optical Society of America.
Motsclés: gold; nanoparticle; article; chemistry; holography; methodology; photometry; refractometry; thermography; ultrastructure; Gold; Holography; Nanoparticles; Photometry; Refractometry; Thermography; Fullfield; Gold Nanoparticles; Heterodyne holography; Local oscillators; Localisation; Low frequency; Metallic nanoparticles; Numerical reconstruction; Photothermal; Photothermal excitation; Pump laser; Refractive index changes; Three dimensions; Heterodyning; Holograms; Nanoparticles; Pumping (laser)


Focusing and amplification of electromagnetic waves by time reversal in an leaky reverberation chamber Davy, M., J. De Rosny, J.C. Joly, and M. Fink Comptes Rendus Physique 11, no. 1, 3743 (2010)
Résumé: In this article, time reversal is used to generate high power microwave pulses from a low power arbitrary wave generator. We use a reverberation chamber with an aperture on the front face and we take advantage of the pulse compression property of time reversal. High amplitude peaks are generated outside the chamber thanks to the long spreading time of the signals inside. We study the amplitude of this peak and the width of the focal spot with respect to the different experimental parameters. A gain of 18 dB compared to a directive antenna of the same aperture is obtained. © 2010 Académie des sciences.
Motsclés: Focal spot; Gain; Reverberation cavity; Time reversal


Transcranial ultrasonic therapy based on time reversal of acoustically induced cavitation bubble signature Gâteau, J., L. Marsac, M. Pernot, J.F. Aubry, M. Tanter, and M. Fink IEEE Transactions on Biomedical Engineering 57, no. 1, 134144 (2010)
Résumé: Brain treatment through the skull with highintensity focused ultrasound can be achieved with multichannel arrays and adaptive focusing techniques such as time reversal. This method requires a reference signal to be either emitted by a real source embedded in brain tissues or computed from a virtual source, using the acoustic properties of the skull derived from computed tomography images. This noninvasive computational method focuses with precision, but suffers from modeling and repositioning errors that reduce the accessible acoustic pressure at the focus in comparison with fully experimental time reversal using an implanted hydrophone. In this paper, this simulationbased targeting has been used experimentally as a first step for focusing through an ex vivo human skull at a single location. It has enabled the creation of a cavitation bubble at focus that spontaneously emitted an ultrasonic wave received by the array. This active source signal has allowed 97 ± 1.1 of the reference pressure (hydrophonebased) to be restored at the geometrical focus. To target points around the focus with an optimal pressure level, conventional electronic steering from the initial focus has been combined with bubble generation. Thanks to stepbystep bubble generation, the electronic steering capabilities of the array through the skull were improved. © 2009 IEEE.
Motsclés: Acoustic beam steering; Acoustic cavitation; Adaptive arrays; Transcranial brain therapy; Acoustic beams; Acoustic cavitations; Adaptive arrays; Brain therapy; Transcranial; Acoustic properties; Acoustic waves; Computerized tomography; Hydrophones; Military photography; Quantum theory; Ultrasonics; Cavitation; acoustic cavitation; acoustics; article; computer assisted tomography; gold standard; high intensity focused ultrasound; mathematical model; microbubble; phantom; skull; transcranial ultra


High voltage time domain response of cMUT membrane: Laser interferometry measurements Sénégond, N., F. Teston, D. Royer, C. Meynier, and D. Certon Physics Procedia 3, no. 1, 10111016 (2010)
Résumé: This paper deals with the understanding of cMUT membrane behavior during a highvoltage excitation. Measurements were performed with a homemade interferometer system. Experimental results in air and fluid (here oil) are discussed.
Motsclés: cMUTs  Laser interferometry; cMUTs  Laser interferometry; High voltage; Highvoltages; Interferometer systems; Membrane behavior; Time domain response; Air; Intensive care units; Ultrasonic transducers; Ultrasonics; Laser interferometry


Achieving antenna isolation within subwavelength directive cavity Ourir, A., R. Abdeddaim, and J. De Rosny Journal of Electromagnetic Waves and Applications 24, no. 23, 219228 (2010)
Résumé: Antenna arrays embedded within a compact FabryPerot cavity have to be optimized to limit interactions between elementary antennas. In this article, we propose to use a superstrate metamaterial to design a highly isolated antenna array. This superstrate is based on the microstrip technology. It is made of an inductive and a capacitive grid respectively etched on the top and the bottom of epoxy plate. Metallic vias are then inserted through the superstrate to connect the two etched grids. This superstrate combined with a metallic ground plane leads to the design of a subwavelength cavity. The proposed cavity allows a significant antenna profile reduction and performance enhancement. More importantly, this structure provides a high isolation for an antenna array. © 2010 VSP.
Motsclés: Antenna isolation; Elementary antenna; FabryPerot cavity; Ground planes; High isolation; Microstrip Technology; Performance enhancements; Profile reduction; Subwavelength; Superstrates; FabryPerot interferometers; Metamaterials; Antenna arrays


A wave superposition method based on monopole sources with unique solution for all wave numbers Leblanc, A., R. K. Ing, and A. Lavie Acta Acustica united with Acustica 96, no. 1, 125130 (2010)
Résumé: A simple solution for the uniqueness problem of the wave superposition method is proposed in this paper. Many authors have pointed out the discrete set of wavenumbers for which the solution of the underlying integral equations is not unique. So far, the usual solutions are theoretically sophisticated and/or numerically disadvantageous. Here, by adding some sources interior to the virtual surface defined by the wave superposition method, the uniqueness problem can be easily removed with low computational effort. Furthermore, dealing with simple monopoles, this method is wellsuited for practical applications. © S. Hirzel Verlag.
Motsclés: Computational effort; Discrete sets; Monopole source; Wave numbers; Wave superposition method; Fluid structure interaction


Walking droplets: A form of waveparticle duality at macroscopic scale? Couder, Y., A. Boudaoud, S. Protière, and E. Fort Europhysics News 41, no. 1, 1418 (2010)

