PET/CT stands for Positron Emission Tomography/Computed Tomography. It combines the metabolic functional information from the PET scan with the anatomical information from the CT image fused into one three dimensional examination of the body. Its use can help diagnose cancer cells, evaluate lesions treated by radiotherapy or chemotherapy and differentiate between inactive necrotic tissue or scar and lesions. PET scans can also be used to determine the blood flow to the heart and the brain. PET uses a small amount of radioactive tracer, Fluorine (FDG) which is added to glucose. The tracer (FDG) is administered by injection to the patient. Since many cancer cells are highly metabolic, the tracer will accumulate with the glucose at a greater rate than the normal surrounding tissues. This radioactivity from the tracer emits positrons as it decays, which are in turn detected by the PET camera. This functional information is then superimposed to the CT image to produce a high quality image of diagnostic accuracy.