Cancerous tissue identified by PET appears as a bright blue blob, and CT pinpoints its location in the colon. The structure of the kidneys (red), bones, and blood vessels--all from a CT scan--are clearly visible as well. PET is used most frequently in oncology exams but also has applications in cardiology and neurology.

GE Healthcare, the manufacturer of the instruments that produced this image, recently introduced two systems that will help researchers develop additional clinical applications. With its ability to monitor cell function, PET is the archetype of the new tools that can monitor our bodies at the cellular or even subcellular scale, says Bruce Hillman of the American College of Radiology Image Metrix.