Automated diameter measurement of vasomotion by cross-correlation

A method to measure automatically and continuously blood vessel diameters in the microcirculation is proposed. After imaging by video microscopy, the window of a video photometric analyzer scans the vessel of interest providing a continuous readout of the optical density along a selected direction in the video scene. The signal is differentiated to find the locations of the vessel walls and is cross-correlated to give their positions in relation to each other, thus mimicking electronically what the eye does in the image-shearing technique. Accuracy is limited to widths between twelve and sixty pixels on the video screen because of restrictions in the precision possible in tracking the peak of maximum cross-correlation. The scanning frequency was 1.2 Hz. Therefore, the method is suitable for quantifying the patterns of vasomotion.