title: Effects of red cell shape and orientation on propagation of sound in blood.
abstract: 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.
mesh_terms: D004912:Erythrocytes; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D009949:Orientation; D014465:Ultrasonics