Measurement of the Velocity of Blood Flow (in vivo) Using a Fiber Optic Catheter and Optical Mixing Spectroscopy

We have measured the velocity of blood flow in the femoral vein of a rabbit by detecting the Doppler shift of laser light introduced into the vein by means of a fiber optic catheter. A 0.5-mm diam optical monofiber inserted in the vein transmits both the incident light and collects the light scattered from the moving erythrocytes. The spectrum of heterodyne beat notes between the local oscillator, which originates at the end of the fiber, and the scattered light are measured using optical mixing spectroscopy.