A system generates medical image data representing smaller vessels including capillaries of a region of patient anatomy. An image data processor identifies pixels of larger vessels in individual images of difference images where the larger vessels have a size exceeding a predetermined threshold size. The image data processor generates an enhanced visualization small vessel image comprising substantially peak luminance values of individual pixels exclusive of pixels of the identified larger vessels. A peak luminance value of an individual pixel is generated in response to a peak luminance value of luminance values of pixels, spatially corresponding to the individual pixel and present in images comprising the plurality of temporally sequential individual difference images. An output processor outputs substantially peak luminance values as a vessel image.
