Stock Photo: PETSCAN. PETSCAN Photo essay from hospital. Department of Nuclear Medicine of the Gustave Roussy Institute, in the French region of Ile-de-France. Exploration with Positron Emission Tomography (PET). PET scan. Cancer diagnosis. Functional imagery technique to detect cancer and follow its evolution. In a PET scan, the patient receives an intravenous injection of radioactive isotopes, creating contrast tracers that are detected by the PET scanner. The radioactive tracer is often 18-Fluor