Positron Emission Tomography (PET) is a nuclear medicine imaging technique in which a radiopharmaceutical or radiotracer, bound to a radioactive material is injected intravenously. This is taken up by many normal and abnormal tissues with ongoing metabolic activity. In other words, it is a functional study. Metabolic activity is high in many normal body tissues. It increases in muscles, especially following physical activity. Tumours and inflammatory lesions also show increased uptake. These lesions, therefore, stand out in the PET scan and can be easily identified. PET scans are coupled with CT or MRI scans. Hence, they can be either PET-CT or PET-MRI scans.