Intra-arterial measurements of the velocity and the average flow of red-blood cells were investigated by means of a fiber-coupled laser Doppler velocimeter based on the self-mixing effect. The velocity of the red cells was calculated from the frequency of the signal that occurs when light, scattered back from a moving object in front of a fiber into a laser-diode cavity, interferes with the laser cavity’s proper mode. These fluctuations occur at the Doppler frequency. The signal was obtained from the photodiode that is present in the laser diode’s housing. Temperature control and stabilization of the diode cavity were introduced to reduce the light-intensity fluctuation that is due to mode hopping of the diode. The velocimeter was calibrated with a rotating disk covered with white paper (nonlinearity of 2.6% for velocities up to 0.4 m/s) and tested <i>in vitro</i> as a fluid velocimeter. The velocimeter was used in <i>in vivo</i> tests on the iliac artery of a 35-kg pig and on the <i>arteria pulmonaris</i> of a healthy calf. The optical fiber was placed in the iliac artery by a basket catheter 4 cm proximal to the bifurcation of the femoral artery. The average arterial blood flow velocity of the red cells were measured upstream and downstream. A special cleaving procedure for the fiber tip in downstream measurement is reported. Blood-velocity measurement is compared with values generated by an ultrasound flowmeter, and a difference of less than 9% is found.
© 2001 Optical Society of America
Lorenzo Scalise, Wiendelt Steenbergen, and Frits de Mul, "Self-Mixing Feedback in a Laser Diode for Intra-Arterial Optical Blood Velocimetry," Appl. Opt. 40, 4608-4615 (2001)