Tuesday, June 10, 2008

Heart Surgeons as Video Gamers

Stereoscopic glasses inspired by video games help surgeons operate on beating hearts.

By Jocelyn Rice

3-D view: Researchers at Children's Hospital Boston are bringing video-game technology into the operating room. Cardiac surgeon Nikolay Vasilyev gives his stereo goggles a test run while performing surgical simulations. The goggles, coupled with a monitor displaying real-time ultrasound data, provide a stereoscopic 3-D view. Vasilyev tested the technology in beating-heart surgery on pigs' hearts and found that it allowed him to patch a hole more efficiently than with traditional 3-D imaging. Credit: Bill O'Connell

Cardiac surgeons have borrowed a 3-D stereoscopic imaging technology from the video-game industry to help them guide their tools during intricate beating-heart surgeries. In tests of the new imaging device, a surgeon was able to more accurately navigate into pigs' hearts and then to more quickly repair the hearts' torn walls. Eventually, the stereoscopic system may make beating-heart surgery more efficient and less dangerous, perhaps expanding its use into relatively complicated heart repairs.

For certain complex heart procedures such as valve repairs, a surgeon must stop the heart and cut it wide open. These surgeries require a heart-lung bypass machine and come with substantial risks to the patient. In recent years, some surgeons are opting to use beating-heart surgery, a less invasive approach that can often obviate the need for heart-lung bypass. But working on complex, delicate internal structures that move with every heartbeat presents major challenges--particularly because without opening the heart and diverting the blood, it's hard for surgeons to see what they're doing.

For several years, a team at Children's Hospital Boston has been developing a real-time 3-D imaging system for use in beating-heart surgery. An ultrasound device gathers a stream of 3-D data and feeds it to a two-dimensional display, indicating depth with shades of gray. By keeping an eye on the display, a surgeon can see inside the heart during the operation.

But while early results of the technology, which has recently found its way into the operating room, have been promising, surgeons found that the two-dimensional display interfered with their depth perception. "If you're navigating a three-dimensionally complicated structure like the heart, where you're making right turns and left turns and going up and down and all over, using a two-dimensional image makes it very difficult," says Pedro del Nido, chief of cardiac surgery at Children's Hospital and leader of the research team.

For a solution, the team looked to an industry that's well versed in creating an ever-improving 3-D experience: video gaming. Recent advances in image-processing technology have allowed game designers to simulate 3-D environments--complete with depth perception--using stereoscopic vision displays. "To address structural heart disease, you need a three-dimensional map with depth perception," says Marc Gillinov, chief experience officer at Cleveland Clinic's Heart and Vascular Institute. "And that's what the stereoscopic glasses give you."

A stereoscopic vision display works by generating a separate, slightly tilted 3-D image for each eye. The monitor rapidly flicks back and forth between the two versions about 70 times per second. Meanwhile, the viewer wears specialized glasses that alternately block the left and right eyes at the same rate. The flickering is fast enough that the eyes, which can only process some 25 to 30 frames per second, don't notice it.