A MUGA (Multiple Gated Acquisition) scan is a test that takes images of your heart as it pumps.  The reason your doctor suggested this test is because some of the chemotherapeutic agents are toxic to the heart. Adriamycin is the most notorious offender.

First the nurse draws blood from you and inserts an iv tube.  She then mixes the radioactive tracer with your blood.  You will have to wait 30 minutes for this to occur as the isotope needs to attach itself to your red blood cells. You are then re-injected with your blood and the radioactive isotope (Technetium 99) through the IV.  You may feel a slight burning when this is injected.

You have to lie on your back for about 40 minutes the last 10 minutes you are asked to put your arms over your head (which is a little uncomfortable) You are placed under a special camera (a gamma camera), which is able to detect the low-level radiation being given off by the Technetium-labelled red cells. Since the red blood cells (including those that are radio-labelled) fill the cardiac chambers, the image produced by the gamma camera is essentially an outline of those chambers. With some fancy computer manipulation, the final product is a movie of the heart beating.

I wrote about my experience with the Muga Scan here 🙂