Cardiac computed tomography, or cardiac CT, is a painless test that uses an x-ray machine to take clear, detailed pictures of your heart. It's a common test for showing problems of the heart. During a cardiac CT scan, the x-ray machine will move around your body in a circle and take a picture of each part of your heart.
Because an x-ray machine is used, cardiac CT scans involve radiation. However, the amount of radiation used is small. This test gives out a radiation dose similar to the amount of radiation you’re naturally exposed to over 3 years. There is a very small chance that cardiac CT will cause cancer.
Each picture that the machine takes shows a small slice of the heart. A computer will put the pictures together to make a large picture of the whole heart. Sometimes an iodine-based dye is injected into one of your veins during the scan to help highlight blood vessels and arteries on the x-ray images.
Figure A shows the position of the heart in the body. The arrow shows the point of view of the cardiac CT image. Figure B is a cardiac CT image showing the coronary arteries on the surface of the heart. This is a picture of the whole heart, put together by the computer.
Cardiac CT is a common test for finding and evaluating:
- Problems in the heart. Iodine-based dye used with a cardiac CT scan can show pictures of the coronary arteries. The coronary arteries are blood vessels on the surface of the heart. If these blood vessels are narrowed or blocked, you may have chest pain or a heart attack. The CT scan also can find problems with heart function and heart valves.
- Problems with the aorta. The aorta is the main artery that carries oxygen-rich blood from the heart to the body. Cardiac CT can detect two serious problems in the aorta:
- Aneurysms, which are diseased areas of a weak blood vessel wall that bulge out. Aneurysms can be life threatening because they can burst.
- Dissections, which can occur when the layers of the aortic artery wall peel away from each other. This condition can cause pain and also may be life threatening.
- Blood clots in the lungs. A cardiac CT scan also may be used to find a pulmonary embolism, a serious but treatable condition. A pulmonary embolism is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lung from the leg.
- Pericardial disease. This is a disease that occurs in the pericardium, a sac around your heart.
Because the heart is in motion, a fast type of CT scanner, called multidetector computed tomography (MDCT), is used to take high-quality pictures of the heart.
Another type of CT scanner, called electron-beam computed tomography (EBCT), is used to detect calcium in the coronary arteries. Calcium in the coronary arteries may be an early sign of coronary artery disease (CAD).