Boris Chayer

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— An approach to estimate blood flow cross-sectional velocity profiles in intravital microscopy videos of post-capillary venules is proposed. Given an image sequence, the cross-section upon which the velocity profile is to be estimated is manually chosen. The velocity of each streamline, assumed perpendicular to the chosen cross-section, is estimated(More)
BACKGROUND The effective orifice area (EOA) is the standard parameter for the clinical assessment of aortic stenosis severity. It has been reported that EOA measured by Doppler echocardiography does not necessarily provide an accurate estimate of the cross-sectional area of the flow jet at the vena contracta, especially at low flow rates. The objective of(More)
3D-ultrasound (US) imaging systems offer many advantages such as convenience, low operative costs and multiple scanning options. Most 3D-US freehand tracking systems are not optimally adapted for the quantification of lower limb arterial stenoses because their performance depends on the scanning length, on ferro-magnetic interferences or because they(More)
Ultrasound characterization of erythrocyte aggregation (EA) is attractive because it is a non-invasive imaging modality that can be applied in vivo and in situ. An experimental validation of the Structure Factor Size Estimator (SFSE), a non-Rayleigh scattering model adapted for dense suspensions, was performed on 4 erythrocyte preparations with different(More)
BACKGROUND We sought to investigate the use of a new parameter, the projected effective orifice area (EOAproj) at normal transvalvular flow rate (250 mL/s), to better differentiate between truly severe (TS) and pseudo-severe (PS) aortic stenosis (AS) during dobutamine stress echocardiography (DSE). Changes in various parameters of stenosis severity have(More)
The aim of this study was to evaluate the effect of the depth of correlation (DOC) on the cross-correlation method (CC) applied to microcirculatory blood flow in vitro. The cross-correlation algorithm was optimized to compute red blood cell velocity profiles in tube flow. Flow rates, estimated by computing the circular integral of mean velocity profiles,(More)
Color Doppler imaging is an established pulsed ultrasound technique to visualize blood flow non-invasively. High-frame-rate (ultrafast) color Doppler, by emissions of plane or circular wavefronts, allows severalfold increase in frame rates. Conventional and ultrafast color Doppler are both limited by the range-velocity dilemma, which may result in velocity(More)
Optical cross-correlation methods have been used to study the motion of red blood cells (RBC) in the microcirculation. To evaluate the precision of such a method to determine RBC velocity profiles, we developped a computational model of the microscopy image formation. The following steps were undertaken: 1) a mechanical model was used to mimic three(More)
Ultrasound ultrafast imaging (UI) allows acquisition of thousands of frames per second with a sustained image quality at any depth in the field of view. Therefore, it would be ideally suited to obtain good statistical sampling of fast-moving tissues using spectral-based techniques to derive the backscatter coefficient (BSC) and associated quantitative(More)
Plane strain tensor estimation using non-invasive vascular ultrasound elastography (NIVE) can be difficult to achieve using conventional focus beamforming due to limited lateral resolution and frame rate. Recent developments in compound plane wave (CPW) imaging have led to high speed and high resolution imaging. In this study, we present the performance of(More)