A method for on-line measurements of red cell velocity in microvessels using computerized frame-by-frame analysis of television images

Abstract

We have used a television signal as the input to a digital computer system to measure red cell velocity in capillaries in a sartorius muscle in frogs. In principle, the velocity was measured in terms of the displacement of red cells and plasma gaps along the capillary (represented here by the shift of an optical density waveform) that occurred in a fixed time interval. Instead of using the conventional spatial cross-correlation of the waveforms, the displacement was determined by means of the absolute differences between the waveforms. The quality of the velocity measurement depended on the optical contrast between the cells and plasma gaps and an index of this quality was determined. The velocity in the capillaries of the frog muscle did not exceed 0.7 mm/sec, but it was demonstrated that, in theory, the velocity could be measured over a range of 0–21 mm/sec. This method is simple, allows further computer analysis of the velocity data and is very useful for studies of the microcirculation.