What is a Viability Scan:Thallium Rest-Rest Perfusion Scan?
A Nuclear Medicine Thallium Viability Scan is a test used to evaluate the blood flow to the heart. After a heart attack (myocardial infarction), some of the heart muscle may be permanently damaged or scarred. Once this occurs, the area affected will cease to function properly. Other parts of the heart may be injured, but not permanently scarred. These areas may be “hibernating”, and may not be detectable through traditional imaging studies, such as an echocardiogram. These damaged areas of the heart may still be “viable”, but may not have completely recovered. As a result, the heart may temporarily function at a much reduced level. You doctor may want to identify these “hibernating” areas because restoring blood flow to that area of the heart may restore proper function and prevent permanent damage from occurring.
A viability scan is accomplished by taking pictures of your heart at various intervals after an injection of a special radioactive drug called Thallium 201. Over a period of time the thallium will be taken into the “good” healthy heart muscle but will not be taken up by any scarred or “bad” heart muscle. Pictures are taken at 30 minutes, 6 hours and the next morning at 24 hours after the injection, to see if the amount of the thallium tracer in the heart has changed.
Why does my cardiologist want me to have a Viability Scan
- Using this test the cardiologist can determine if there is an adequate amount of this “hibernating” or “stunned” tissue, verses heart tissue that is permanently damaged. This will help the cardiologist determine which type of treatment is best suited for your case.
Who will be performing my test?
- An imaging technologist with special training in the use of radioactive drugs (Nuclear Medicine Technologist) will be taking the images of your heart using a machine called a Gamma Camera.
Is there any kind of preparations or instructions that I need to follow?
- There is no required preparation for this scan. You may eat before arrival but it is best if you can just eat a very light meal such as a bagel, toast or small bowl of cereal. Caffeinated beverages such as coffee and tea are allowed prior to this procedure.
What can I expect?
Check In: Prep and Initial Imaging
- Once you have checked in you will be taken into the prep area by one of our Nuclear Medicine Technologists. They will verify information from your record and explain the procedure to you.
- An intravenous line (IV Line) will also need to be placed into a vein in your arm or hand. This is used to administer the radioactive drug used for imaging. It is required for this procedure or we will not be able to take the pictures of your heart.
- You will be given an injection of a radioactive tracer (Thallium 201). This allows the cardiologist to see the blood flow to your heart muscle. This is the only injection that is required for this procedure.
- You will be asked to return to the waiting room and to drink about 12 to 16 oz of liquid. There is a water cooler in the hallway for your use. There is also a refrigerator on the counter near the exit door that contains diet and regular non caffeinated soda. You may drink one of these instead of water. Please use the rest room at any time.
- To allow for the proper imaging, a 25 to 30 minute wait is required before imaging can be started. You will be called back to the imaging area when it is time for your pictures.
- Imaging is accomplished using a special type of radiation detector called a gamma camera. This detects the injected tracer in the heart muscle and transfers it to a computer. The computer processes these images into thin slices so that the doctor can look at blood flow into your heart muscle.
- You will sit on the imaging chair and bring your arms over your head. It is very important that at least the left arm be raised above the head. If it is by your side it may prevent some of the tracer in the heart from reaching the detector. We can attempt to do the scan with your arms at your side but this may seriously affect the ability of the cardiologist to properly evaluate your exam.
- The imager will be positioned close to your chest and will slowly rotate around your body in a half circle. The picture takes approximately 15 – 20 minutes and it is very important that not move at all.
- Once the picture is completed you will be able to leave but you must return to the department in 4 to 6 hours for a second set of pictures.
- The technologist will instruct you at what time you should return for your second set of pictures.
- You will also need to return the next morning for a final set of pictures. You will be given a return time by the nuclear technologist after the second set of images is completed.
- Since this study requires multiple sets of imaging, it is a very time consuming procedure. The first set of images, from check in to check out, may take about 2 hours to complete. An additional hour is required for each of the repeat pictures: in the afternoon, and the next morning. For this reason, it is best that you not schedule any other appointments on the same day as this testing.
What are the risks?
- In recommending this procedure your doctor has balanced the benefits and risks of the test against the benefits and risks of not proceeding. Your doctor believes there is a benefit of you having this test.
- There is a small radiation exposure from the radioactive drug, but this is generally no more than you would receive from any other X-Ray procedure such as a CAT Scan or some X-Ray Procedures.