A method to quantify the vascular irregularity of aortoiliac arteries is provided. Inner wall and/or outer wall outlines of a vessel of interest are determined. The cross sectional area is determined for the area outlined by each outline. Using this cross sectional area a shape is selected that has substantially the same area as the outline. Subsequently, the shape is fitted to the outline. In one aspect, the irregularity index is calculated as the ratio of the outline and the outline of the fitted shape. In another aspect, the irregularity index is calculated as the ratio of at least a part of the outline and the outline of the fitted shape that corresponds to the same part of the outline. The irregularity index is visualized using a color scheme, a range of numbers, or a set of labels.