Method and apparatus for measuring flow motions in a fluid

Details Method and apparatus for measuring flow motions in a fluid Method and apparatus for measuring flow motions in a fluid

1979-10-23

1984-10-16

Howell, Kyle L.

Surgery

Truss

Pad

128691, A61B 502

Patent

active

044768753

ABSTRACT:
For determining flow motions in a fluid containing light scattering particles, in particular for determining the blood circulation in the superficial blood vessels in a tissue, a section of the fluid is illuminated with monochromatic light from a laser (1). Light scattered from particles in the fluid and from any surrounding stationary structures is gathered from two, at least partially separated but mutually adjacent regions of the illuminated section of the fluid and transmitted separately to two separate photodetectors (5, 5'). From the output signal of each photodetector a signal is derived, which contains the beat frequency components resulting from interference between light components received by the photodetector, which have different frequencies due to the Doppler frequency shift of the light scattered by moving particles. The two signals so derived from the output signals of the two photodetectors are subtracted from each other and the signal resulting from this subtraction is used as a measure of flow motions in the fluid.

REFERENCES:
patent: 3511227 (1970-05-01), Johnson
patent: 3822695 (1974-07-01), Takayama
patent: 4109647 (1978-08-01), Stern et al.
Stern, M. D., "In vivo Evaluation of Microcirculation by Coherent Light Scattering" Nature, vol. 254, Mar. 1975, pp. 56-58.
Watkins, D. et al., "An Instrument to Measure Cutaneous Blood Flow Using the Doppler Shift of Laser Light," IEEE Trans. Biomed Engrg, vol. BME-25, No. 1, Jan. 1978, pp. 28-33.
Stern, M. D. et al., "Measurement of Local Tissue Blood Flow by Laser Doppler Spectroscopy", Abstract, Proc. of Federation of Amer. Societies for Exper. Biology, 60th Ann. Meeting, Anaheim, Cal., Apr. 1976.

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