Retinal vessel circulation patterns visualized from a sequence of computer-aligned angiograms.

PURPOSE To present a computer method that can be used to combine the images from a sequence of fluorescein angiograms of the retinal microcirculation so that a composite image can be generated and a color image illustrating circulation at all points in the vascular network can be computed. This should enable more accurate comparison of retinal vascular occlusions that occur during cardiopulmonary bypass surgery. METHODS Photographic negatives of the macular region from two angiographic sequences, one taken before surgery and the other taken just before the end of bypass, were digitized, background shade corrected, and registered. Composite images were generated as minimum projection images and the filling images generated from parameters of a smooth curve fit to the filling data at every point. RESULTS The composite images showed a filling pattern that more accurately reflected the maximum fluorescence at every point than any single image. The images generated from the filling data provide a new way to visualize and quantify changes in the retinal circulation. CONCLUSIONS The technique demonstrates that problems arising from selection of a single frame from a filling sequence can be overcome by combining images. The technique used to generate the color-coded filling image should prove useful for any image sequence in which differential filling is of interest.