Light from the VisEn probes is captured in pictures taken from multiple angles by a near-infrared camera. These pictures are then mathematically reconstructed into a 3-D image, which is projected for context onto a simple white-light photograph of the animal. Other molecular imaging systems that use fluorescent probes can't provide 3-D images and can't penetrate deep into the animal. VisEn's technology, says Peterson, is most comparable to positron emission tomography (PET). But PET scanning uses radioactive probes, requires a particle accelerator, and can't measure protein activity level.

Kay Macleod, assistant professor of cancer research at the University of Chicago, is using the probes to study the course of breast cancer in mice. If she were using other imaging methods, says Macleod, she would have to perform surgery on the animals in order to get the laser and camera close enough to the tumors. VisEn's infrared imaging system reveals tumors deep inside mice, eliminating the need for surgery.

VisEn is applying to the Federal Drug Administration for permission to begin testing the imaging method in humans to look for cancer and atherosclerosis. One challenge is that while the near-infrared light emitted by the probes can pass all the way through mice, it's absorbed as it passes through humans. Peterson says that the company will develop endoscopes and catheters to bring near-infrared cameras close to human tissues in hopes of guiding surgeons to the ones that are diseased.