BASIC RESEARCH FOR DEVELOPMENT OF LASER SPECKLE BLOOD VELOCIMETER USING A SELF-MIXING LASER DIODE

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(1) Blood Flow Measurement by Autocorrelation Function Method :The inverse of the correlation time calculated from the autocorrelation function of a speckle signal obtained from a self-mixing laser diode (SM-LD) shows a linear dependence on a blood flow velocity with a far smaller offset frequency.(2) Comparison of the SM-LD Speckle Blood Flow Velocimeter with Two Commercially Available Blood Flow Velocimeters :A time dependence of the mean frequency with an averaging time 2 seconds for a human finger which was measured by the SM-LD blood flow velocimeter showed a similar tendency to a time dependence of the blood flow velocity measured by a laser Doppler velocimeter. During the measurement the blood flow was changed in 3 phases by adjusting the pressure of the cuff wound around the upper arm. Furthermore, another time dependence of the mean frequency with an averaging time 0.02 seconds obtained by the SM-LD velocimeter had fairly good coincidence with a time dependence of the blood fl … More ow velocity obtained by an ultrasonic Doppler blood flow velocimeter, which shows repeated velocity peaks due to the heart beat.(3) Calibration of the SM-LD Speckle Blood Flow Velocimeter :An obtained slope parameter was 13 Hz/mm/s in a velocity range 40 mm/s to 130 mm/s. The 13Hz/mm/s was smaller than a slope parameter 22Hz/mm/s obtained for sheep total blood filled in a gutter of a rotating turn table. While the 13Hz/mm/s was nearly equal to 15Hz/mm/s obtained for the sheep total blood flowing through a silicon tube with an inner and external diameter 1 mm and 2mm, respectively.(4) Simulating Experiment Using a Skin Phantom and a Tube :From the experiment using both a skin phantom plate made of gelatin containing distributed and fixed total sheep blood and intralipid and a silicon vein tube, a measurable skin depth was confirmed less than 1mm and the measured velocity was assumed due to the blood flow in capillaries of the finger. Reduction of the artifact effect is one of future research subject. Less