Enhanced image detail using continuity in the MIP Z-buffer: Applications to magnetic resonance angiography

In this paper a new algorithm is presented for the segmentation and display of blood vessels from images obtained with magnetic resonance angiography (MRA) and other three-dimensional (3D) angiographic imaging techniques. The algorithm developed is based on the observation that vessels are strongly evident in the maximum intensity projection (MIP) Z-buffer as regions of hi gh continuity and low local roughness. Roughness is measured here by the mi nimum chi(2) value of a low-order local least-squares fit in the principal directions through each point in the MIP Z-buffer, Although some background pixels in the Z-buffer exhibit low local roughness, the size of the connec ted region is nearly always much smaller than even the very smallest vessel s that appear in the MIP image. It is shown that by applying connectivity t o the regions of low roughness, there is nearly complete separation between vascular detail and background. When connectivity is further applied in th e original 3D image, vascular bed segmentation becomes nearly complete. The algorithm consists of three basic steps: a) determination of the minimum l ocal roughness at each point in the MIP Z-buffer; b) connection of all neig hboring points of low local roughness; and c) connection of all points in t he original 3D image matrix that are connected to the points determined In the MIP Z-buffer and that are above an intensity threshold, The algorithm a s presented is not optimized but demonstrates a very strong potential for i mproved portrayal of vascular detail, (C) 2000 Wiley-Liss, Inc.