Visit Halle's home at the Surgical Planning Lab at the Harvard Medical School.


































Rendering Adds Radiance To Everyday Life

By Danialle Weaver

Michael Halle uses computer graphics to help doctors get under your skin--all before they ever reach for a scalpel.

About twice a week, Halle, a researcher, lecturer and instructor at Boston's Brigham and Women's Hospital, an affiliate of Harvard Medical School, turns routine diagnostic medical scans into detailed images of the human body for doctors there. He does this by using a computer graphics technique known as rendering, which is the process of adding realistic surfaces to geometric models by computing how light bounces off various surfaces.

"We start with scans that a lot of people get, such as those from MRI (magnetic resonance imaging) or CAT (computerized axial tomography) scans, and we build three-dimensional models from them," he explains. "This helps the doctors plan their surgery ahead of time, so they know what lies below the surface. For example, they'll know there's a blood vessel right below the surface of the skin." With that knowledge, the doctors can work around the vessel and avoid puncturing it.

Surgical planning renderings courtesy Surgical Planning Lab, Brigham and Women's Hospital.


Sometimes, Halle says, the computer that does the rendering calculations is outfitted with a probe, placed on a cart, and wheeled into the operating theater. The probe has infrared light emitting diodes on it, and they can be tracked by a set of line cameras. The probe is used to register the patient to the data. "Once we know the relationship between the patient and the data, we can draw a computer-generated probe on a CRT that corresponds to the real probe. The surgeon can then point to the patient and see the corresponding location in the data," he says.

In other words, the doctor can use the probe to point to the area of concern in the patient's body and then have the image of that area show up directly on the computer screen. "They can see exactly where they're going, and if they're removing a tumor, this gives them a sense that they either got all of it or there's more somewhere," he says. That could mean the difference between life and death.

As Halle's experience shows, computer graphics techniques such as rendering are already making a real difference in the lives of ordinary people. "This is not just a cool thing to do, or an intellectual pursuit," he says. "Without applications, what's the point? You can't go home and tell your mom the relevance of what you're doing."



