ULTRASOUND SCATTERING FROM BLOOD WITH HEMATOCRITS UP TO 100-PERCENT

The backscattering coefficient of saline suspensions of porcine red bl ood cells was measured for hematocrits up to about 90%. It was found t hat the coefficient peaks at approximately 15%, but then, contrary to what a simple ''gap theory'' might suggest, it decays smoothly to zero , without showing another peak at high hematocrits. A one-dimensional (1-D) slab scattering model, in which the number of slabs per unit Len gth represents the hematocrit and whose thickness and acoustical prope rties are similar to red cells/plasma, was also used to investigate th e relation between the backscattered power and hematocrit. Monte-Carlo simulations performed for randomized boundary conditions show a simil ar relation to that of the 3-D system. The experimental data is compar ed to the Percus-Yevick theory for the packing of hard spheres, and th e simulated data is compared to the Percus-Yevick theory for infinite slabs.