A thallium scan is conducted to map the flow of blood to the heart. The following HealthHearty write-up provides information on this diagnostic procedure.
A thallium scan is conducted to measure the flow of blood to the heart muscles to determine if the heart is getting adequate blood supply. It involves the use of a special perfusion-scanning camera and thallium-201, which is a radioactive substance that is injected into the bloodstream through an intravenous line, in small doses. This test can help in the identification of areas with irregular blood flow. The scan is conducted twice. It is first done when the patient is fully rested, and again after a physical activity. This is to determine the flow of blood during rest and stress periods. Records are maintained and compared to check the flow of blood.
For this procedure, the patient has to lie on his/her back on a table. A large gamma scintillation camera is placed above the patient’s chest. Here’s the procedure for this test:
- After the injection site is cleaned, thallium or the radioactive tracer is injected intravenously.
- The radioactive substance travels through the bloodstream and is absorbed by the healthy heart muscle tissue.
- Pictures are generated using the gamma scintillation camera with the gamma rays that are emitted by the radioactive tracer.
- On the scan, the areas where the substance is not absorbed due to irregular blood flow, appear to be different than areas with proper blood flow.
- The second part of the test is done while the patient is on a treadmill or on a stationary bike to check the flow of blood to the heart muscles under stress.
- In case of people who cannot get on a treadmill or a bike, a special drug might be injected that produces the same effect as that of exercise on the heart. In some patients, adenosine is used to stimulate stress conditions for a thallium stress test.
- Thallium shows up on pictures taken subsequently, highlighting the areas with low blood flow.
- This chemical stress test is an effective myocardial perfusion method to detect problems related to blood flow in the heart. The areas which are not highlighted or have poor imaging are known as ‘defect’ areas with little or no blood supply.
- In the preparation routine, the patient is advised not to drink caffeine or products laced with caffeine.
- Small round metal objects known as electrodes are attached to the body to monitor the vital signs.
- The test is conducted under hospital settings, under medical supervision.
- This methods can also be used to measure the blood flow to the brain.
This test can certainly prove beneficial in checking for irregular blood flow in the heart or brain. The side effects are rare. Since thallium is a radioactive metal, it is administered in small doses. In rare cases, one might have an extreme reaction, or other adverse effects such as shortness of breath, changes in blood pressure, headaches, etc., might be experienced. Women should inform the doctor if they are pregnant or breastfeeding to avoid the risks.
A thallium scan is mostly done to diagnose conditions like coronary artery disease. It is one of the most effective ways to determine if the supply of blood to a localized area is irregular.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.