Effects of red cell shape and orientation
on propagation of sound in blood

Avtar S. Ahuja and William R. Hendee

Department of Radiology, University of Colorado Medical Center, Denver, Colorado 80262
In this paper, the red blood cell (RBC) is assumed to have an oblate spheroidal shape and
the same volume (87 micrometer3) and about the same sphericity index (0.7) as a typical
human RBC. The acoustic field is assumed to be either parallel or perpendicular to the axis
of symmetry of the spheroid, and a wave equation is formulated for a dilute RBC
suspension. Because of the small density difference between the RBC and plasma (about
5%), the assumption of spherical shape of the RBC suffices for computation of the velocity
and the scattering of sound in blood. For all practical purposes, scattering of sound in blood
follows Rayleigh's law of scattering. However, the viscous absorption coefficient at 1 MHz
for a spheroidally shaped RBC oscillating broadside and edgewise to an acoustic field is
about 40% and 136%, respectively, of that for a spherically shaped RBC. These results
illustrate the significant effects of RBC shape and orientation on the viscous loss of sound
energy in blood.


Source
http://www.ncbi.nlm.nih.gov/pubmed/927389