Modeling and analysis of ultrasound backscattering by sphericalaggregates and rouleaux of red blood cells

摘要

The present study concerns the modeling and analysis of ultrasoundnbackscattering by red blood cell (RBC) aggregates, which undernpathological conditions play a significant role in the rheology of bloodnwithin human vessels. A theoretical model based on the convolutionnbetween a tissue matrix and a point spread function, representing,nrespectively, the RBC aggregates and the characteristics of thenultrasound system, was used to examine the influence of the scatterernshape and size on the backscattered power. Both scatterers in the formnof clumps of RBC aggregates and rouleaux were modeled. For allnsimulations, the hematocrit was kept constant at 10%, the ultrasoundnfrequency was 10 MHz, the insonification angle was varied from 0 ton90°, and the scatterer size (diameter for clumps and length fornrouleaux) ranged from 4 Μm to 120 Μm. Under Rayleigh scattering bynassuming a Poisson distribution of scatterers in space, the ultrasoundnbackscattered power increased linearly with the particle volume. Fornnon-Rayleigh scatterers, the intensity of the echoes diminished as thenscatterer volume increased, with the exception of rouleaux at an anglenof 90°. As expected, the backscattered power was angularly dependentnfor anisotropic particles (rouleaux). The ultrasound backscattered powerndid not always increase with the size of the aggregates, especially whennthey were no longer Rayleigh scatterers. In the case of rouleaux, thenanisotropy of the backscattered power is emphasized in the non-Rayleighnregion