Arie Kaufman, a computer scientist at the State University of New York at Stony Brook, likes to say that whenever he steps into his lab, the experience is akin to "discovering a new continent."
It's less a continent and more another dimension; Kaufman is a pioneer in volume visualization (VolVis), a technology that takes 2-D data from CAT scans, MRIs, PETs, and X-rays and renders them as 3-D images. VolVis's users can then, on screen, peel the outer layers of the brain, search for tumors, change the angle of view, or magnify areas of concern, all without touching a scalpel.
The implications of the technology are staggering, from medical applications to environmental science to national defense to entertainment. Already, VolVis is enabling researchers to see inside the brain in greater detail than ever before, to delve into the cells and synapses that make thought and memory possible, to concoct more realistic flight-simulation programs, to measure ground-water flows, and to search for oil reserves.
And all this is just the tip of the arithmetic. VolVis relies on a series of algorithms to simulate "ray tracing": how particles in a volume emit, absorb, or refract light. The process works by taking an object, already traditionally represented in triangles (these then form 2-D images), and translating it into volume elements called "voxels." When individual rays pass through each voxel, the data are accumulated and displayed on screen. With VolVis, you can get the inside scoop on just about everything.
Since Kaufman's university does not budget for research, he's had to turn to other sources. The National Science Foundation and the US Department of Energy each awarded him US$100,000 for volume visualization research.
On the Stony Brook campus' Howard Hughes Medical Institute (no affiliation to Hughes Aircraft), volume visualization is used to analyze the circuits within brain cells. Says Paul Adams, a Hughes researcher, "We're gearing up to look at one of the central questions in neurobiology: Where is memory stored? This is a 3-D question. You need a technique that allows you to look for small changes in many parts of the brain simultaneously. VolVis is playing a key role in this. For us, it's vital that this tool has come along."
But the MIPS-greedy VolVis will have to be souped up if it's to out-maneuver 2-D surface-based visualization systems. At Brigham and Women's Hospital in Boston (an affiliate of Harvard University Medical School), both techniques are used to detail patients' anatomies before, during, and after surgery.
"Whether or not volume-based systems are better isn't clear," says Bill Lorensen, a graphics engineer with GE who has been working with doctors at Brigham for seven years. "As for surface-based systems, you can always see one surface, but you can't see through it, so it's not clear what surface is in front of another. Similarly, with an X-ray, it's hard to see one surface behind another. The volume techniques can't produce images as quickly, so Brigham and Women's, for now, is using both, although surface-based systems win out because they're faster." But Kaufman expects VolVis to improve over time. "Even now we can see that this technology will revolutionize the field of computer graphics."
VolVis software, instructions, manuals, and conversion utilities are available to researchers free of charge over the Internet (volvis@cs.sunysb.edu).
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