3-DIMENSIONAL DURING ARTERIAL PORTOGRAPHY - COMPARISON OF 3 RENDERINGTECHNIQUES

The three most common techniques for three-dimensional reconstruction are surface rendering, maximum-intensity projection (MIP), and volume rendering. Surface-rendering algorithms model objects as collections o f geometric primitives that are displayed with surface shading. The MI P algorithm renders an image by selecting the voxel with the maximum i ntensity signal along a line extended from the viewer's eye through th e data volume. Volume-rendering algorithms sum the weighted contributi ons of all voxels along the line. Each technique has advantages and sh ortcomings that must be considered during selection of one far a speci fic clinical problem and during interpretation of the resulting images . With surface rendering, sharp-edged, clear three-dimensional reconst ruction can be completed on modest computer systems; however, overlapp ing structures cannot be visualized and artifacts are a problem. MIP i s computationally a fast technique, but it does not allow depiction of overlapping structures, and its images are three-dimensionally ambigu ous unless depth cues are provided. Both surface rendering and MIP use less than 10% of the image data. In contrast, volume rendering uses n early all of the data, allows demonstration of overlapping structures, and engenders few artifacts, but it requires substantially more compu ter power than the other techniques.