The advent of "minimally invasive" surgery, performed with slender instruments through tiny incisions, has meant less trauma and faster healing for patients. But the technique requires surgeons to watch a video or ultrasound screen while operating to see what's going on underneath the skin-an awkward proposition for the surgeon. A head-mounted virtual-reality apparatus, developed at the University of North Carolina and now in clinical trials, could offer doctors a more natural view and allow for faster, safer operations.

The trial-the first conducted with such a device-will involve 24 women undergoing breast tissue biopsies. A surgeon dons headgear incorporating glasses-like displays and two cameras mounted in front of her eyes. A computer merges ultrasound information flowing from a probe held to the patient's skin with video taken by the cameras, showing the operation site. This combination gives the surgeon a view into the body that corresponds with her natural perspective. What's more, the system tracks every twist and turn of the surgeon's head using ceiling-mounted cameras. Software adjusts for these movements to keep the ultrasound and video components of the surgeon's view in sync.

Harvard Medical School's Ferenc Jolesz, director of image-guided therapy at Boston's Brigham and Women's Hospital, says the North Carolina device "may lead to fundamental change in surgical visualization." The technology does, however, have competition. Siemens is developing a similar device and is now seeking an appropriate clinical trial.

The North Carolina device might take a decade to reach operating rooms, says computer scientist Henry Fuchs, who led the team that developed it. So far, a surgeon working with Fuchs has performed four operations; Fuchs hopes that others will be completed this year. After that, he aims to seek an industrial partner to further develop the technology.