Blood cell banding in ultrasonic standing wave fields: A physical analysis

Blood cell flow can be arrested in living tissue by exposing the blood vessels to ultrasound in a stationary wave field. The cells form into bands at half wavelength intervals in the blood vessels. This phenomenon is described, and the forces that may be involved are discussed. The forces considered include standing wave radiation pressure, inter-cellular forces and Oseen forces. A computer model is described and the computed trajectories of cells under the action of these forces are shown.