Biology subjects

Denis, L.

Publications and source records attributed to Denis, L..

3 recordsLinked to original sources

bioRxiv2024

RF Channel-Based Adaptive Beamforming for 3D Ultrasound Localization Microscopy

Ultrasound Localization Microscopy (ULM) has been applied in various preclinical settings and in the clinic to reveal the microvasculature in deep organs. However, most ULM images employ standard Delay-and-Sum (DAS) beamforming. In standard ULM conditions, lengthy acquisition times are required to fully reconstruct small vessels due to the need for spatially isolated microbubbles, resulting in low temporal resolution. When microbubbles are densely packed, localizing a point spread function with significant main and side lobes becomes challenging due to matrix arrays low signal-to-noise ratio and spatial resolution. In this work, we applied adaptive beamforming such as high order DAS known as (pDAS), Coherence Factor (CF), Coherence Factor with Gaussian Filtering (CFGF), and statistical interpretation of beamforming (iMAP) to provide a more complete 3D ULM maps in vitro and in vivo (rat kidney). Specifically, the CF and 1MAP adaptive beamformers achieved higher resolution (32.9 microns and 27.2 microns respectively), as measured by the Fourier Shell Correlation (FSC), compared to the standard DAS beamformer, which had an FSC value of 38.6 microns.

physiology↗

bioRxiv2024

3D Transcranial ultrasound localization microscopy reveals major arteries in the sheep brain

ObjectiveStroke, a leading cause of mortality and disability globally, demands swift and accurate diagnosis for effective treatment. Although MRI and CT scans serve as conventional methods, their accessibility remains a challenge, prompting exploration into alternative, portable, and non-ionizing imaging solutions like ultrasound with reduced costs. While Ultrasound Localization Microscopy (ULM) displays potential in high-resolution vessel imaging, its 2D constraints limit its emergency utility. Materials and MethodsThis study delves into the feasibility of 3D ULM with multiplexed probe for transcranial vessel imaging in sheep brains, emulating human skull characteristics. Three sheep underwent 3D ULM imaging, compared with angiographic MRI, while skull characterization was conducted in vivo using ultrashort bone MRI sequences and ex vivo via micro CT. Results and conclusionsThe study showcased 3D ULMs ability to highlight vessels, down to the Circle of Willis, yet within a confined 3D field-of-view. Future enhancements in signal, aberration correction, and human trials hold promise for a portable, volumetric, transcranial ultrasound angiography system. Summary statement3D Ultrasound localization microscopy, using a low-frequency matrix probe, enables transcranial reconstruction of the main vessels in sheep brains.

physiology↗

bioRxiv2023

Whole organ volumetric sensing Ultrasound Localization Microscopy for characterization of kidney structure

Glomeruli are the filtration units of the kidney and their function relies heavily on their microcirculation. Despite its obvious diagnostic importance, an accurate estimation of blood flow in the capillary bundle within glomeruli defies the resolution of conventional imaging modalities. Ultrasound Localization Microscopy (ULM) has demonstrated its ability to image in-vivo deep organs in the body. Recently, the concept of sensing ULM or sULM was introduced to classify individual microbubble behavior based on the expected physiological conditions at the micrometric scale. In the kidney of both rats and humans, it revealed glomerular structures in 2D but was severely limited by planar projection. In this work, we aim to extend sULM in 3D to image the whole organ and in order to perform an accurate characterization of the entire kidney structure. The extension of sULM into the 3D domain allows better localization and more robust tracking. The 3D metrics of velocity and pathway angular shift made glomerular mask possible. This approach facilitated the quantification of glomerular physiological parameter such as an interior traveled distance of approximately 7.5 {+/-} 0.6 microns within the glomerulus. This study introduces a technique that characterize the complete kidney phisiology which can serve as a method to facilite pathology assessment. Furthermore, its potential for clinical relevance could serve as a bridge between research and practical application, leading to innovative diagnostics and improved patient care.

physiology↗