A filtering method and apparatus for selectively filtering a gray scale angiographic image volume (54) that images vascular structures and that also contains extraneous non-vascular contrast is disclosed. A minimum vessel width parameter W_min (70) is selected. A maximum vessel width parameter W_max (132) is selected. A range of widths (66) are selected such that each vessel width parameter W_i (194) lies between W_min (70) and W_max (132) inclusive. For each W_i (194), an image I_i(x,y,z) (198) is generated that selectively retains imaged vascular structures of diameter W_i (194). The images I_i(x,y,z) (198) are combined to form a filtered image I_F(x,y,z) (64) that selectively images the vascular structures.