Use of digital cross-correlation for on-line determination of single-vessel blood flow in the mammalian kidney.

The empirical relationship between erythrocyte velocity (Vrbc) and mean blood velocity (Vblood) was studied in quartz capillaries by television microscopy using the dual-slit technique. A newly designed desktop digital on-line cross-correlator was combined with a computer to determine Vrbc. The accuracy of the digital correlator was tested for velocities ranging from 0 to 3 mm/sec and compared with values determined using an analog tracking correlation device. There was good agreement. Small-bore glass tubes with diameters ranging from 12 to 26 micron were perfused with suspensions of erythrocytes having hematocrits between 10 and 37%. The relationship between mean blood velocity and erythrocyte velocity in these quartz tubes was found to be Vblood = 0.88 Vrbc - 0.11, and was independent of diameter and hematocrit within the range investigated. The mean ratio for Vrbc/Vblood was 1.42 +/- 0.06.