| Autor: |
Savéry, David, Cloutier, Guy |
| Předmět: |
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| Zdroj: |
IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control; Jan2005, Vol. 52 Issue 1, p94-103, 10p, 7 Diagrams, 3 Charts |
| Abstrakt: |
When flowing at a low shear rate, blood appears hyperechogenic on ultrasound B-scans. The formation of red blood cell (RBC) aggregates that also alters blood viscosity is the microscopic mechanism explaining this acoustical phenomenon. In this study, Monte Carlo simulations were performed to predict how RBC clustering increases ultrasound scattering by blood. A bidimensional Gibbs-Markov random point process parameterized by the adhesion energy € and an anisotropy index v was used to describe RBC positions for a hematocrit H = 40%. The frequency dependence of the backscattering coefficient χ(&fnof) was computed using Born approximation. The backscattering coefficient χ0 at 5 MHz and the spectral slopes nx and ny (χ &isin ƒnx or ƒny) measured, respectively, when the insonification is parallel and perpendicular with the RBC cluster axis were then extracted. Under isotropic conditions, χ0 increased up to 7 dB with ϵ and nx = ny decreased from 4.2 to 3.4. Under anisotropic conditions, the backscattering was stronger perpendicularly to aggregate axis, resulting in nx < ny. The anisotropy in scattering appeared more pronounced when ϵ or v increased. These two dimensional results generally predict that low-frequency blood backscatter is related to cluster dimension, and higher-frequency properties are affected by finer morphological features as anisotropy. This numerically establishes that ultrasound backscatter spectroscopy on a large frequency range is pertinent to characterize in situ hemorheology. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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