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A rendering technique is presented that generates integrated intensity projection images for volumetric data with visual enhancement of the data within a region-of-interest. Animated displays result form moving this region through the data volume, either interactively or following a trajectory generated from the data itself. Enhancement is provided by applying a radially symmetric weighting function to each point within the data set based upon its position relative to the center of the region-of-interest and the viewpoint. The resultant integrated value is scaled using the cumulative weighting applied along the projection vector to set the displayed pixel intensity. By bounding the region- of-interest and maintaining unity weighing outside this volume, the rendering process may be decomposed into base and supplemental components. Both may be generated off-line. Alternately, interactive data exploration may be performed using either a pre-processed base projection or, to provide more flexibility, real-time generation of both components. In addition, rendered images may be comprised of base and supplemental components obtained from heterogeneous data volumes, the difference arising either due to processing of a single-modality data ste or by the use of registered multi-modality dat sets. Images are presented showing application of this technique to medical volumetric data sets obtained from MR, CT and ultrasound scanning. PC based software implementation on current hardware allows rendering rates that support interactive exploration of 2563 voxel data sets. Automatic path generation uses segmentation to isolate relevant structures followed by skeletonization to reduce these volumes to path segments. Linking these segments presents a number of problems if the resultant path is to be both efficient and traversed without distracting jumps or other artifacts. The use of back-tracking and the movement tempo are currently being investigate. Future research directions include: optimization of the technique to take account of human visual perception; cache-optimized rendering implementation; the use of color; and more powerful path generation strategies.
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