The test is actually divided into three parts: Imaging at rest, a treadmill stress test, and imaging after exercise. There are two common types of isotope used: thallium and technetium. Some laboratories use a "dual isotope" technique, where thallium is used for the resting images and technetium is used for the stress pictures. Depending upon the isotope and protocol for the laboratory, resting images may be obtained either before stress or two to four hours after stress.
Your heart rate and blood pressure will be monitored throughout the test, and the ECG is displayed continuously on a monitor and printed every minute. About one minute prior to termination of exercise, the perfusion tracer or isotope is injected into your vein. After a brief wait (to allow the tracer to be taken up by the heart muscle) you will be placed under a scanning camera. The scanning camera rotates around the patient's chest, stopping to take individual pictures. You will need to lay flat and still during the scanning period which takes approximately 11 to 20 minutes, depending upon the type of scanning camera. The pictures or images are fed into a computer, which reconstructs them as "slices" of a three dimensional heart.