Color-coded depth information in volume-rendered magnetic resonance angiography
Örjan Smedby, Karin Edsborg, John Henriksson · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2004
Magnetic Resonance Angiography (MRA) and Computed Tomography Angiography (CTA) data are usually presented using Maximum Intensity Projection (MIP) or Volume Rendering Technique (VRT), but these often fail to demonstrate a stenosis if the projection angle is not suitably chosen. In order to make vascular stenoses visible in projection images independent of the choice of viewing angle, a method is proposed to supplement these images with colors representing the local caliber of the vessel. After preprocessing the volume image with a median filter, segmentation is performed by thresholding, and a Euclidean distance transform is applied. The distance to the background from each voxel in the vessel is mapped to a color. These colors can either be rendered directly using MIP or be presented together with opacity information based on the original image using VRT. The method was tested in a synthetic dataset containing a cylindrical vessel with stenoses in varying angles. The results suggest that the visibility of stenoses is enhanced by the color information. In clinical feasibility experiments, the technique was applied to clinical MRA data. The results are encouraging and indicate that the technique can be used with clinical images.