1. A method for performing vascular segmentation of 3D images with adaptive parameter setting in a geodesic active contour (GAC) segmentation process, the method comprising: (a) acquiring 3D input images containing voxels as units of graphic information defining points in 3D space; (b) performing active contour segmentation on said 3D input images, wherein said segmentation evolves a closed curve/surface through a combination of different forces; (c) mapping gradient and speed function by using shape information as prior knowledge to guide the mapping between the gradient and speed function; (d) enhancing gradients at boundaries of vessel-like regions in the 3D input images; (e) suppressing gradients inside or outside vessel-like regions in the 3D input images; (f) iteratively correcting a shape-based parameter image using result of gradient mapping as it provides complementary information to said shape information; and (g) outputting segmentation contours for vessels found in the 3D input images; (h) wherein said method is performed by executing programming on at least one computer processor, said programming residing on a non-transitory medium readable by the computer processor.