Laser Doppler Measurements of Localized Pulsatile Fluid Velocity

An optical Doppler velocimeter utilizing optical heterodyning techniques was used to measure radial velocity profiles of pulsatile flow in a cardiovascular circulation model. The light source was a single-mode frequency-stabilized He-Ne CW laser (6328 Å, 0.1 mW). The laser beam was focused to a 30-¿m in diameter spot in the flow stream. Polystyrene spheres 0.73 ¿m in diameter, suspended in distilled water, were used as light scatterers. The optical signal beam contained Doppler-shifted scattered light. The reference beam was split from the source beam in one configuration; in a second configuration an acoustical frequency modulator was installed in the reference beam pathway as part of a directional flow measurement system. The circulation model consisted of an artificial heart, a Windkessel model, a peripheral resistance, a capillary model, a reservoir, and an optical glass window section. The flow test section was positioned by a three-dimensional finely adjustable holder. From 10 to 34 point measurements were obtained to plot one velocity profile, which covered 95 percent of the tube diameter.