If ProScan-A works, it could revolutionize the way physicians diagnose HIV disease progression. Based on cancer diagnostic technology, ProScan-A combines a protein that binds to HIV and a nontoxic radioisotope that emits signals detectable with a special camera. After a person with HIV is injected with the radioisotope, it clings to HIV infected cells and the virus itself, and shows physicians the volume and concentration of HIV in the body, said company spokesman Joel Sendek. A phase I trial of ProScan-A, the brainchild of Progenics Pharmaceuticals, is underway at the Memorial Sloan-Kettering Cancer Center in New York City to determine the procedure's safety. Eventually, Progenics hopes to develop a database incorporating thousands of different readins that will assist doctors in diagnosing the health of a positive person based on the ProScan-A image, Sendek said.