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A thallium scan is a test that uses a radioactive substance (known as a tracer) to produce images of the heart muscle. When combined with an exercise test, the thallium scan helps determine if areas of the heart do not receive enough blood. 


The exercise thallium test is especially useful in diagnosing coronary artery disease, the presence of blockages in the coronary arteries. These arteries supply oxygen to the heart muscle. Tracers, other than thallium, can be used for this type of scan. Your Baylor Scott & White Cardiology Consultants of Texas doctor will decide if your situation warrants a different type of tracer.

Before The Test

  • You will receive an instruction sheet that pertains to the specific type of tracer your physician plans to use.  If you have any questions, please ask your doctor or the nuclear technician.
  • You may be asked to fast (not eat or drink anything) for three to four hours or longer prior to your exam. If you cannot fast, or are diabetic, ask your BSW Cardiology Consultants of Texas doctor or nurse for special instructions. 
  • You will be instructed not to have food or drink prior to the test that contains caffeine. For example, coffee, tea, colas (even "caffeine-free"), and chocolate foods all contain different amounts of caffeine. 
  • Be sure to notify our office nurse or nuclear tech of all the medicines you are taking. Some medicines may affect the test results. 
  • Wear loose, comfortable clothing that is suitable for exercise. You should also wear comfortable walking shoes or tennis shoes. 
  • Before the test, you will be given an explanation of the test and you will be asked to sign a consent form. Feel free to ask any questions about the procedure. 

During The Test

  • The test has two parts: the exercise imaging portion and the rest imaging portion.
  • Several electrodes (small sticky patches) will be placed on your chest to obtain an electrocardiogram (ECG).  This will record your heart's electrical activity. 
  • An intravenous (IV) line will be started in a vein in your arm.  This will allow injection of the radioactive tracer during exercise. 
  • Depending on the type of exam that is ordered, you will be exercising several minutes on a treadmill.  If you cannot walk on a treadmill, then a prescribed medication will be injected over several minute periods.  In either case, the purpose is to increase the workload being placed on your heart. 
  • You will be instructed to report any symptoms, such as chest pain, shortness of breath, or dizziness.  Try to exercise for as long as you are able to, as this will increase the accuracy of the test. 
  • Tell the nuclear technician when you are almost to the point when you can no longer exercise.  At this point, the tracer will be injected into the intravenous line.  You will be asked to continue to exercise for another minute or so after the injection.
  • Imaging portion: You will then lie flat on a special table under a scanning camera. Several pictures of the heart will be taken at various angles.  You should remain still while the pictures are being taken.  This part can take up to 20 minutes. 
  • After this initial set of pictures, you will be asked to return in 2 to 4 hours to have additional pictures taken without repeating the exercise.  These images are compared to the images obtained during the first part of the test. The technician will give you specific instructions regarding when to return, and what food you can eat. 

After The Test

  • No sedation is given during this test; therefore, you will be able to drive home directly after the test. 
  • The BSW​ Cardiology Consultants of Texas doctor conducting the test may be able to give you preliminary results before you leave.  However, a complete interpretation usually takes several days. 
  • In addition to being called, a copy of your test results is sent to your referring physician. 
  • This test generally provides more information than an exercise stress test.  This will help your doctor make an accurate diagnosis and develop a treatment plan that is best for you.