Mapping Biological Current Densities with Ultrafast Acoustoelectric Imaging: Application to the Beating Rat Heart.
Berthon, B., A. Behaghel, P. Mateo, P. M. Dansette, H. Favre, N. Ialy-Radio, M. Tanter, M. Pernot, and J. Provost.
IEEE Transactions on Medical Imaging 38, no. 8 (2019): 1852–1857.
Résumé: © 1982-2012 IEEE. Ultrafast acoustoelectric imaging (UAI) is a novel method for the mapping of biological current densities, which may improve the diagnosis and monitoring of cardiac activation diseases such as arrhythmias. This paper evaluates the feasibility of performing UAI in beating rat hearts. A previously described system based on a 256-channel ultrasound research platform fitted with a 5-MHz linear array was used for simultaneous UAI, ultrafast B-mode, and electrocardiogram (ECG) recordings. In this paper, rat hearts (n = 4) were retroperfused within a Langendorff isolated heart system. A pair of Ag/Cl electrodes were positioned on the epicardium to simultaneously record ECG and UAI signals for imaging frame rates of up to 1000 Hz and a mechanical index of 1.3. To account for the potential effect of motion on the UAI maps, acquisitions for n = 3 hearts were performed with and without suppression of the mechanical contraction using 2,3-butanedione monoxime. Current densities were detected for all four rats in the region of the atrio-ventricular node, with an average contrast-to-noise ratios of 12. The UAI signals' frequency matched the sinus rhythm, even without mechanical contraction, suggesting that the signals measured correspond to physiological electrical activation. UAI signals appeared at the apex and within the ventricular walls with a delay estimated at 29 ms. Finally, the signals from different electrode positions along the myocardium wall showed the possibility of mapping the electrical activation throughout the heart. These results show the potential of UAI for cardiac activation mapping in vivo and in real time.
Mots-Clés: Biological current density imaging; heart; real-time imaging; ultrafast acoustoelectric imaging; ultrafast ultrasound imaging; ultrasound
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Cramér-Rao analysis of lifetime estimations in time-resolved fluorescence microscopy.
Bouchet, D., V. Krachmalnicoff, and I. Izeddin.
Optics Express 27, no. 15 (2019): 21239–21252.
Résumé: © 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement Measuring the lifetime of fluorescent emitters by time-correlated single photon counting (TCSPC) is a routine procedure in many research areas spanning from nanophotonics to biology. The precision of such measurement depends on the number of detected photons but also on the various sources of noise arising from the measurement process. Using Fisher information theory, we calculate the lower bound on the precision of lifetime estimations for mono-exponential and bi-exponential distributions. We analyse the dependence of the lifetime estimation precision on experimentally relevant parameters, including the contribution of a non-uniform background noise and the instrument response function (IRF) of the setup. We also provide an open-source code to determine the lower bound on the estimation precision for any experimental conditions. Two practical examples illustrate how this tool can be used to reach optimal precision in time-resolved fluorescence microscopy.
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Ultrasensitive Doppler as a tool for the diagnosis of testicular ischemia during the Valsalva maneuver: a new way to explore varicoceles?
Rocher, L., J. L. Gennisson, J. Barranger, A. Rachas, A. Criton, V. Izard, M. Bertolloto, M. F. Bellin, and J. M. Correas.
Acta Radiologica 60, no. 8 (2019): 1048–1056.
Résumé: © The Foundation Acta Radiologica 2018. Background: Varicocele is among the most common causes of male infertility because of various mechanism, including hypoxia. Purpose: To evaluate testicular vascularization (TV) with ultrasensitive Doppler before and during the Valsalva maneuver (VM) and correlate TV changes to varicocele’s spermatic venous reflux graduated by color Doppler. Material and Methods: From January to February 2016, 69 men (135 testis) referred for scrotal ultrasound were prospectively enrolled. An institutional review board approved the study. As gold standard, the spermatic venous reflux in the supratesticular region was assessed with color Doppler ultrasound and graded from 0 to III. A new ultra-sensitive Doppler (USD) sequence was performed on testicular parenchyma in an axial view. The TV changes before and during the VM were qualitatively graded from 0 to 2 using a visual scale by consensus. The vessels surface was quantified using customized MATLAB® software, and compared to the testicular delineated surface, resulting in a vessels surface ratio (VSR). The absolute and relative VSR difference before and during the VM was calculated. The qualitative scale and the quantitative VSR changes were compared with the spermatic venous reflux grade using an analysis of variance. Results: A strong correlation has been found between the spermatic venous reflux grade and TV decrease during the VM using USD, for qualitative graduation as well as for quantitative measurement (P < 0.0001). Conclusion: TV assessed by USD decreased significantly during the VM in patients with varicocele; this decrease was significantly associated with spermatic venous reflux grade.
Mots-Clés: male infertility; Ultrafast imaging; ultrasensitive Doppler; varicocele
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Viral metagenomic analysis of the cheese surface: A comparative study of rapid procedures for extracting viral particles.
Dugat-Bony, E., J. Lossouarn, M. De Paepe, A. S. Sarthou, Y. Fedala, M. A. Petit, and S. Chaillou.
Food Microbiology 85 (2020).
Résumé: © 2019 Elsevier Ltd The structure and functioning of microbial communities from fermented foods, including cheese, have been extensively studied during the past decade. However, there is still a lack of information about both the occurrence and the role of viruses in modulating the function of this type of spatially structured and solid ecosystems. Viral metagenomics was recently applied to a wide variety of environmental samples and standardized procedures for recovering viral particles from different type of materials has emerged. In this study, we adapted a procedure originally developed to extract viruses from fecal samples, in order to enable efficient virome analysis of cheese surface. We tested and validated the positive impact of both addition of a filtration step prior to virus concentration and substitution of purification by density gradient ultracentrifugation by a simple chloroform treatment to eliminate membrane vesicles. Viral DNA extracted from the several procedures, as well as a vesicle sample, were sequenced using Illumina paired-end MiSeq technology and the subsequent clusters assembled from the virome were analyzed to assess those belonging to putative phages, plasmid-derived DNA, or even from bacterial chromosomal DNA. The best procedure was then chosen, and used to describe the first cheese surface virome, using Epoisses cheese as example. This study provides the basis of future investigations regarding the ecological importance of viruses in cheese microbial ecosystems.
Mots-Clés: Cheese rind; Viral metagenomic; Viral particles extraction procedure
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