A video system for measuring the blood flow velocity in microvessels

Capillary blood cell velocity in finger nailfold: characteristics and reproducibility of the local cold response

The characteristics and reproducibility of nailfold capillary blood cell velocity (CBV) of the local cold response was evaluated in 30 cases by video-microscopy using a flying-spot technique. CBV, as well as flow stop duration during cooling, from a first and second test was significantly (P less than 0.05) reproducible, whether or not the test was repeated after 60 min or after an interval of 12 weeks. Because of interindividual variations in rest CBV, and a better reproducibility of the flow stop duration, this last parameter is more useful in clinical practice for follow-up evaluations of the local cold response test. The usefulness of the flying-spot generator for rapid and accurate measurement of CBV in finger nailfold capillaries is demonstrated in normal subjects and patients with primary Raynaud syndrome during a local cooling test.

CCD line-scan image sensor for the measurement of red cell velocity in microvessels

A device for measuring red cell velocities in transilluminated microvessels has been developed using a 256 element charge-coupled device (CCD) line scan sensor. An image of the moving red cells is focussed on the device so that it senses optical data along the flow axis. Paired sets of data, separated by a fixed time interval, are sampled by an A/D converter operating at 1 MHz, and transferred to a dedicated microcomputer employing the MC68000 (Motorola Inc.) microprocessor. Velocity is computed from the detected spatial shift occurring in the time between data sets. The computed velocity is converted to an analogue voltage. Calibration is linear, the system is direction-sensitive and it can detect zero motion.

Methods to measure blood flow velocity of red blood cells in vivo at the microscopic level

Several methods to measure red blood cell velocity in microvessels by electronic means are discussed. Signals are generated by the red blood cells present in the microscopic image of the microvessels. These signals can be converted to obtain an output signal proportional to the actual red blood cell velocity. The method of spatial filtering by interlacing gratings is discussed in terms of a filter with an input signal. Adaptation of optical factors that might improve the velocity measurement is obtained by a mathematical analysis. Different methods of correlation are presented. The temporal correlation (dual slit and video window) and spatial correlation methods are discussed in relation to factors influencing the quality of the correlogram, the peak of which is proportional to red blood cell velocity. The conversion of red blood cell velocity to volume flow is put in perspective.