Positron Emission Tomography

What is a PET scan?

PET (Positron Emission Tomography) is one of the newest, most advanced methods for studying the heart. Like an X-ray, PET is painless and noninvasive. This means no surgery or opening of the body is required. Unlike X-rays, PET does much more than just show a picture of the heart. PET actually gives an image of the health of the heart.

What are PET scans used for?

There are two reasons to have a PET scan:

1. To check the health of the coronary arteries (the vessels that supply blood to the heart). If arteries are narrowed or blocked, the heart muscle can be starved of oxygen. This is known as coronary artery disease.

2. To check the heart muscle. If heart tissue has died because of a heart attack, the heart will not work as well. The doctor can use this information to plan treatment. PET can be an alternative to invasive tests such as cardiac catheterization, in which a thin tube is threaded through a vein and into the heart.

How do PET scans differ from other heart tests? Clinical studies have shown that PET scans are more accurate than other widely used tests such as ECG (electrocardiogram) stress testing and SPECT (single photon emission computed tomography). These tests are associated with "false positive" results, which are results that show coronary heart disease where none exists. False positives can lead to people undergoing unnecessary procedures. Because PET scans are so accurate, they are often used to confirm other tests if a false positive is suspected.

Who should have a PET scan? Only a doctor can decide if PET is the right heart test for a particular patient. If you are interested in PET as an alternative to some other heart test such as stress testing or cardiac catheterization, talk to your doctor.

Who should not have a PET scan? As a rule, the following people are excluded from having a PET scan. Be sure to check with your doctor.

- Women who are pregnant or who think they might be pregnant.
- Nursing mothers.
- People who have recently had a stroke or heart attack.
- People with a history of asthma or lung disease.
- People who are allergic to caffeine, theophylline, aminophylline or dipyridamole.

How does the test work? The test takes place inside a PET scanner, which is a large machine shaped like a ring standing on edge. The person having the test lies on a bed. The bed passes slowly through the center of the ring. A small amount of liquid, known as a "tracer," is introduced into an arm vein. The person receives an injection of a drug that increases blood flow through the normal arteries. However, the blood flow will not be increased in arteries that are blocked or in tissue that is damaged. The differences in blood flow are detected by the PET scanner, which creates a picture of the blood flow to the heart tissue.