Parker D L, Chapman B E, Roberts J A, Alexander A L, Tsuruda J S
Department of Radiology, University of Utah, Salt Lake City, Utah 84132, USA.
J Magn Reson Imaging. 2000 Apr;11(4):378-88. doi: 10.1002/(sici)1522-2586(200004)11:4<378::aid-jmri5>3.0.co;2-#.
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 high continuity and low local roughness. Roughness is measured here by the minimum chi2 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 connected region is nearly always much smaller than even the very smallest vessels that appear in the MIP image. It is shown that by applying connectivity to the regions of low roughness, there is nearly complete separation between vascular detail and background. When connectivity is further applied in the original 3D image, vascular bed segmentation becomes nearly complete. The algorithm consists of three basic steps: a) determination of the minimum local roughness at each point in the MIP Z-buffer; b) connection of all neighboring points of low local roughness; and c) connection of all points in the 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 as presented is not optimized but demonstrates a very strong potential for improved portrayal of vascular detail.
本文提出了一种新算法，用于从磁共振血管造影（MRA）和其他三维（3D）血管造影成像技术获取的图像中分割和显示血管。所开发的算法基于这样的观察结果：在最大强度投影（MIP）Z缓冲器中，血管作为高连续性和低局部粗糙度的区域非常明显。这里通过在主方向上对MIP Z缓冲器中每个点进行低阶局部最小二乘拟合的最小卡方值来测量粗糙度。虽然Z缓冲器中的一些背景像素表现出低局部粗糙度，但连通区域的大小几乎总是比MIP图像中出现的最小血管还要小得多。结果表明，通过对低粗糙度区域应用连通性，血管细节和背景之间几乎完全分离。当在原始3D图像中进一步应用连通性时，血管床分割几乎可以完成。该算法由三个基本步骤组成：a）确定MIP Z缓冲器中每个点的最小局部粗糙度；b）连接所有低局部粗糙度的相邻点；c）连接原始3D图像矩阵中所有与MIP Z缓冲器中确定的点相连且强度高于阈值的点。所提出的算法尚未优化，但展示了在改善血管细节描绘方面的巨大潜力。
