In hospitals or on hospital dramas on TV, you've probably seen patients undergoing radiation therapy for cancer, and doctors ordering PET scans to diagnose patients. These are part of the medical specialty called nuclear medicine. Nuclear medicine uses radioactive substances to image the body and treat disease. Nuclear medicine looks at both the physiology (functioning) and the anatomy of the body in establishing diagnosis and treatment.

In this edition of How Stuff Works, we will explain some of the techniques and terms used in nuclear medicine. You'll learn how radiation helps doctors see deeper inside the human body than they ever could.