Evaluation and clinical application of the flying spot method in clinical nailfold capillary TV-microscopy

A video flying spot device was developed for the measurement of red blood cell velocity for clinical skin capillarscopy. The method relies on the advancing of a light spot on the TV-screen utilizing horizontal and vertical synchronized video pulses. Practical evaluation showed satisfactory accuracy in comparison to the frame-to-frame technique as well as reproducibility in the velocity range from 0 to 1.1 mm/s (correlation coefficients = 0.94). The advantage of this device lies in its simplicity and low cost. The suitability for application in the clinical laboratory is demonstrated in normal subjects and patients with Raynaud's phenomenon during a local cooling test using both the flying spot and the frame-to-frame technique.