On-line measurement of the dynamic velocity of erythrocytes in the cerebral microvessels in the rat

Abstract A technique using incident light microscopy, two-slit transit time photometry and a cross-correlation computer for on-line measurement of the velocity of erythrocytes in the cerebral microvessels of normal rat brain is described. The system projects the dark-field illuminated microscopic image of a pial microvessel exposed by a cranial window onto the ends of two optical fibers which are coupled to two photodiodes. The photometric signals produced are connected to a cross-correlation computer which computes the transit time continuously. The transit time is then converted electronically to a voltage proportional to the velocity of the erythrocyte and the voltage is recorded by a strip-chart recorder. The system has been directly calibrated against erythrocytes in whole blood in a moving channel and the accuracy is within ±2%. The normal erythrocyte velocities in different orders of the pial microvasculature were systematically measured and the data presented.