Like a stress echo test, nuclear cardiology studies produce images of the heart at work (during exercise) and at rest. During a test, you are given an injection of a small dose of a harmless radioactive tracer. Then you spend time exercising on a treadmill or stationary bicycle and then resting. A specialized camera (called a "gamma camera") detects the tracer as it passes through the chambers of your heart, creating the pictures. The pictures may reveal problems in heart muscle and blood vessels, especially when the images of the heart at work and at rest are compared.