Last updated: 02/17/2009

The MUGA scan is a series of images that demonstrate the flow of blood through the heart, providing information about heart muscle activity. Before images are taken, a radionuclide is injected into the bloodstream, a process that requires two injections...

in most health care facilities. The first injection contains a chemical that adheres to red blood cells, and the second contains a radioactive tracer (Tc99m) that attaches to that chemical. Alternatively, the two chemicals can be mixed together first and then injected, but the material tends to accumulate in bone and may obscure the heart.

The pictures are taken via gamma camera driven by a computer program that times the images, processes the information, and performs the mathematical calculations to provide ejection fraction and demonstrate wall motion. Images are obtained at various intervals during the cardiac cycle. Electrodes are placed on the patient so that a time frame can be established, for example, the time period between each "wave" (a part of the cardiac cycle seen on an EKG). The time frame is divided into several intervals, or "multiple gates." The result is a series of pictures showing the left and right ventricles at end-diastole (when the heart is dilated and filled with blood) and end-systole (when the heart is contracted and blood is being pumped out), and a number of stages in between.

A MUGA scan is performed in a hospital nuclear medicine department or in an outpatient facility. It takes approximately 30 minutes to one hour. The patient lies down on a bed alongside the gamma camera, receives the radionuclide injections, and multiple images are taken. If a stress study is indicated, the rest study is performed first. In a stress study, the patient usually lies on a special bed fitted with a bicycle apparatus. While an image is being recorded, the patient is asked to cycle for about two minutes, then the resistance of the wheels is increased. After two more minutes of exercise, another image is obtained and the resistance is increased again. Blood pressure and ECG are monitored during the procedure. After the stress portion is finished, one more resting, or recovery, study is obtained.