2014 
A hybrid FDTDRayleigh integral computational method for the simulation of the ultrasound measurement of proximal femur. Cassereau, D., P. Nauleau, A. Bendjoudi, J.  G. Minonzio, P. Laugier, E. Bossy, and Q. Grimal. Ultrasonics 54, no. 5 (2014): 1197–1202.
Résumé: The development of novel quantitative ultrasound (QUS) techniques to measure the hip is critically dependent on the possibility to simulate the ultrasound propagation. One specificity of hip QUS is that ultrasounds propagate through a large thickness of soft tissue, which can be modeled by a homogeneous fluid in a first approach. Finite difference time domain (FDTD) algorithms have been widely used to simulate QUS measurements but they are not adapted to simulate ultrasonic propagation over long distances in homogeneous media. In this paper, an hybrid numerical method is presented to simulate hip QUS measurements. A twodimensional FDTD simulation in the vicinity of the bone is coupled to the semianalytic calculation of the Rayleigh integral to compute the wave propagation between the probe and the bone. The method is used to simulate a setup dedicated to the measurement of circumferential guided waves in the cortical compartment of the femoral neck. The proposed approach is validated by comparison with a full FDTD simulation and with an experiment on a bone phantom. For a realistic QUS configuration, the computation time is estimated to be sixty times less with the hybrid method than with a full FDTD approach. © 2013 Elsevier B.V. All rights reserved.
MotsClés: DORT method; Femoral neck; Guided waves; Semianalytic; Simulation


Measurements of ultrasound velocity and attenuation in numerical anisotropic porous media compared to Biot's and multiple scattering models. Mézière, F., M. Muller, E. Bossy, and A. Derode. Ultrasonics 54, no. 5 (2014): 1146–1154.
Résumé: This article quantitatively investigates ultrasound propagation in numerical anisotropic porous media with finitedifference simulations in 3D. The propagation media consist of clusters of ellipsoidal scatterers randomly distributed in water, mimicking the anisotropic structure of cancellous bone. Velocities and attenuation coefficients of the ensembleaveraged transmitted wave (also known as the coherent wave) are measured in various configurations. As in real cancellous bone, one or two longitudinal modes emerge, depending on the microstructure. The results are confronted with two standard theoretical approaches: Biot's theory, usually invoked in porous media, and the Independent Scattering Approximation (ISA), a classical firstorder approach of multiple scattering theory. On the one hand, when only one longitudinal wave is observed, it is found that at porosities higher than 90% the ISA successfully predicts the attenuation coefficient (unlike Biot's theory), as well as the existence of negative dispersion. On the other hand, the ISA is not well suited to study twowave propagation, unlike Biot's model, at least as far as wave speeds are concerned. No free fitting parameters were used for the application of Biot's theory. Finally we investigate the phaseshift between waves in the fluid and the solid structure, and compare them to Biot's predictions of inphase and outofphase motions. © 2013 Elsevier B.V. All rights reserved.
MotsClés: Biot's theory; Cancellous bone; Fast and slow waves; Multiple scattering; Porous media


Improving photoacousticguided optical focusing in scattering media by spectrally filtered detection. Chaigne, T., J. Gateau, O. Katz, C. Boccara, S. Gigan, and E. Bossy. Optics Letters 39, no. 20 (2014): 6054–6057.


Light Focusing and TwoDimensional Imaging Through Scattering Media using the Photoacoustic TransmissionMatrix with an Ultrasound Array. Chaigne, T., J. Gateau, O. Katz, E. Bossy, and S. Gigan. Optics Letters 39, no. 10 (2014): 2664–2667.
Résumé: We implement the photoacoustic transmission matrix approach on a twodimensional photoacoustic imaging system, using a 15 MHz linear ultrasound array. Using a black leaf skeleton as a complex absorbing structure, we demonstrate that the photoacoustic transmission matrix approach allows to reveal structural features that are invisible in conventional photoacoustic images, as well as to selectively control light focusing on absorbing targets, leading to a local enhancement of the photoacoustic signal.


Controlling light in scattering media noninvasively using the photoacoustic transmission matrix. Chaigne, T., O. Katz, A. C. Boccara, M. Fink, E. Bossy, and S. Gigan. Nature Photonics 8 (2014): 58–64.
Résumé: Optical wavefront shaping has emerged as a powerful tool for manipulating light in strongly scattering media. It enables diffractionlimited focusing and imaging at depths where conventional microscopy techniques fail. However, to date, most examples of wavefront shaping have relied on direct access to the targets or implanted probes, and the challenge is to apply it noninvasively inside complex samples. Recently, ultrasonictagging techniques have been utilized successfully, but these allow only small acoustically tagged volumes to be addressed at each measurement. Here, we introduce an approach that allows the noninvasive measurement of an optical transmission matrix over a large volume, inside complex samples, using a standard photoacoustic imaging setup. We demonstrate the use of this matrix for detecting, localizing and selectively focusing light on absorbing targets through diffusive samples, as well as for extracting the scattering medium properties. Combining the transmissionmatrix approach with the advantages of photoacoustic imaging opens a path towards deeptissue imaging and light delivery utilizing endogenous optical contrast.


Accurate measurement of guided modes in a plate using a bidirectional approach. Moreau, L., J.  G. Minonzio, J. Foiret, E. Bossy, M. Talmant, and P. Laugier. Journal Of The Acoustical Society Of America 135, no. 1 (2014): EL15–EL21.
Résumé: Measuring guided wave propagation in long bones is of interest to the medical community. When an inclination exists between the probe and the tested specimen surface, a bias is introduced on the guided mode wavenumbers. The aim of this study was to generalize the bidirectional axial transmission technique initially developed for the first arriving signal. Validation tests were performed on academic materials such a bonemimicking plate covered with either a silicon or fatmimicking layer. For any inclination, the wavenumbers measured with the probe parallel to the waveguide surface can be obtained by averaging the wavenumbers measured in two opposite directions.

