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Cardiac blood flow (cardiac perfusion) can be evaluated by either PET/CT or Nuclear Medicine (using SPECT scanners). A radioactive molecule that has been engineered to mimic the blood flow within the heart is injected into a patient. Depending on the radioactive molecule used, a patient is then scanned on either at PET/CT or SPECT scanner to assess cardiac blood flow and any possible blockages in the cardiac blood vessels.
Thallium, technetium sestamibi (Cardiolite), technetium tetrofosmin, N-13 ammonia, and/or FDG are all radiotracers that can be injected into patients to scan and image cardiac blood flow and tissue damage. The scan estimates the amount of blood reaching the heart muscle during rest and exercise. It is typically done to determine the cause of unexplained chest pain or to determine the location and amount of injured heart muscle after a heart attack.
For this test, a radioactive substance called a tracer is injected into a vein in your arm. The tracer is often technetium tetrofosmin (Myoview) or N-13 ammonia but can be several other products that are available. Once the radioactive tracer has been injected into the bloodstream, a SPECT or PET/CT scanner is used to view the amount of the tracer that reaches the heart muscle. As the tracer moves through the heart muscle, areas that have good blood flow absorb the tracer. If an area of heart muscle does not adequately absorb the tracer, it means either that the blood flow is severely reduced (ischemia) or there has been a previous heart attack. The tracer remains in the body temporarily (less than a day) before it is eliminated, usually in the urine or stool (feces).
Cardiac scans often involve making two sets of images: rest images and stress images. Rest images are taken while the person is resting and stress images are taken after the heart has been exercised (treadmill) or by using a medication called Lexiscan, adenosine, dipyridamole (Persantine), or dobutamine (Dobutrex). Then the resting images and the stress images are compared. Medication stress testing may be done instead of exercise stress testing for older adults and people with conditions that may make exercise difficult, such as those who are obese or those with COPD, peripheral vascular disease, spinal cord injury, arthritis, or multiple sclerosis.