High Speed Digital Video Capillaroscopy: Nailfold Capillary Shape Analysis and Red Blood Cell Velocity Measurement

Nailfold capillaroscopy has been shown to reflect microvascular disturbances mainly in connective tissue diseases, and the development of video capillaroscopy made it possible to determine capillary red blood cell velocity by measuring the displacement of plasma gaps between red cells. We improved both temporal and spatial resolutions of video capillaroscopy by developing the high speed digital video capillaroscopy, integrating high speed digital video camera, deep-focus zoom lens, appropriate light source and light collecting adaptor. The first objective of this study is to present the novel method for quantitative capillary shape analysis by using the level-set method. The capillary radius distribution along the capillary center line is obtained and described by the level-set function. Based on this mathematical description of capillary shape, more rigorous definition of the capillary red blood cell velocity than the conventional method is discussed. The second objective of this study is to propose the innovative measurement method of red blood cell velocity in nailfold capillary, and then the possibility of tracking the individual red blood cell movement, not only in the axial direction but also lateral direction, in human nailfold capillary is discussed