Volume seedlings

Recent advances in software and hardware technology have made direct ray-Traced volume rendering of 3-d scalar data a feasible and effective method for imaging of the data's contents. The time costs of these rendering techniques still do not permit full interaction with the data, and all of the parameters effecting the resulting images. This paper presents a set of real-Time interaction techniques which have been developed to permit exploration of a volume data set. Within the limitation of a static viewpoint, the user is able to interactively alter the position and shape of an area of interest, and modify local viewing parameters. A run length encoded cache of volume rendering samples provides the means to rerender the volume at interactive rates. The user locates and plants "seeds" in areas of interest through the use of data slicing and isosurface techniques. Image processing techniques applied to volumes ( i.e. volume processing), can then automatically form regions of interest which in turn modify the rendering parameters. This "region growing" of "seedlings" incrementally alters the image in real-Time providing further visual cues concerning the contents of the data. These tools allow interactive exploration of internal structures in the data which may be obscured by other imaging algorithms. Magnetic Resonance Angiography (MRA) provides a driving application for this technology. Results from preliminary studies of MRA data are included.