Positron Emission Tomography is an invaluable and perhaps most important tool for assessing cancer in vivo. Dr. Burrell provides a quick overview of the types of imaging used in oncology, specifically describing the role of PET in each stage of the therapy cycle. A brief history of PET is given, together with the basic physics and a glance at radiopharmaceutical use in oncology. The potential role of PET from diagnosis through staging, therapy planning, post-therapy evaluation and followup is discussed and many case studies presented.