The thallium scan is a nuclear imaging test that shows how well blood flows into your heart while you’re exercising or at rest. This test is also called a cardiac or nuclear stress test. During the procedure, a liquid with a small amount of radioactivity called a radioisotope is injected into one of your veins. According to the Heart and Stroke Foundation, “The radioisotope will flow through your bloodstream and end up in your heart. Once the radiation is in your heart, a special camera called a gamma camera can detect the radiation and reveal any issues your heart muscle is having”.
You can prepare for a thallium scan by not eating or drinking for at least three hours before your test, or abstain from having any tobacco, alcohol, caffeinated beverages or over-the-counter medications in the 24 hours before the procedure. If you have diabetes or any other metabolic diseases, talk to your doctor about the severity of the diseases and what kinds of prescriptions you take. Also talk about any allergies which might give a negative reaction to the stress test.
The procedure of the thallium scan is the following: you will be asked to lie on a table, then a small amount of thallium (a radioactive tracer) is injected into a vein in your arm. A camera will then measure the amount of the thallium that is carried through your bloodstream and into your heart. The parts of your heart that receives a small amount of good blood supply will pick up the tracer. The tracer will not pick up poor blood supply, so it will appear as dark spots on the scan. This procedure is a relatively low-risk scan. The amount of radiation is absorbed into the body is about the same amount of radiation released from a CT scan.
Reasons why doctors might make you take a thallium scan is listed in the following: if they suspect your heart isn’t getting enough blood flow when it’s under stress — for example, when you exercise. If you have chest pain, worsening angina, or a previous heart attack are usually the main reasons why doctors take thallium scans. Other reasons include: to check how well your medications are doing, to determine whether a surgery or procedure was successful, or to determine if any metabolic diseases such as diabetes have reacted negatively to your blood and immune system. Scans can show the size of your heart chambers, how effectively your heart pumps, how well coronary arteries supply your heart with blood (known as myocardial fusion), and if your heart is damaged from previous heart attacks.
There are two parts of the thallium scan, a rest portion and an exercise portion. According to Healthline, “ During this resting part of the test, you lie down for 15 to 45 minutes while the radioactive material works its way through your body to your heart. You then lie down on an exam table with your arms above your head, and a gamma camera above you takes pictures”. In the exercise portion of the test, you walk on a treadmill or pedal an exercise bicycle. Most likely, your doctor will ask you to start slowly and progressively pick up the pace into a jog. You may need to run on an incline to make it more challenging. If you’re unable to exercise, your doctor will give you a medication that stimulates your heart and makes it beat faster. This simulates how your heart would act during exercise. According to Healthline, “Your blood pressure and heart rhythm are monitored while you exercise. Once your heart is working as hard as it can, you’ll get off the treadmill. After about 30 minutes, you’ll lie down on an exam table again. The gamma camera then records pictures that show the flow of blood through your heart. Your doctor will compare these pictures with the set of resting images to evaluate how weak or strong the blood flow to your heart is.
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