Enhancement of Temporally Variable Features in Nailfold Capillary Patterns

Analysis of the condition of blood capillaries in the nailfold is complicated by the fact that gaps in the flow of blood cells results in temporal variability in their appearance. At a single instant the capillaries may be incomplete, but integration of the information from several successive video frames renders the whole capillary visible. This paper shows that combining the information from the video frame sequence by subtracting a multiple of the standard deviation from the mean value for each pixel, improves the signal to noise ratio of variable features when compared with the mean image or using minimum projection.