Computed tomography (CT or CAT scan) is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.
In standard X-rays, a beam of energy is aimed at the part of the body being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a regular X-ray, a lot of detail about internal organs and other structures is not available.
In computed tomography, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure, and provides much greater detail. The X-ray information is sent to a computer which interprets the X-ray data and displays it in 2-dimensional (2D) form on a monitor.
A new technology, called ultrafast CT scan, is now being used to diagnose heart disease. Ultrafast CT, or electron-beam computed tomography (EBCT) can take multiple images of the heart within the time of a single heartbeat, thus providing much more detail about the heart's function and structures, and also greatly decreasing the amount of time required for a study. Ultrafast CT scans can detect very small amounts of calcium within the heart and the coronary arteries. This calcium has been shown to indicate that lesions that may eventually block off one or more coronary arteries and cause chest pain, or even a heart attack, are in the beginning stages of formation. Thus, ultrafast CT scanning may be used by physicians as a means to diagnose early coronary artery disease in certain people, especially in individuals who have no symptoms of the disease.
Other related procedures that may be used to assess the heart include resting and exercise electrocardiogram (ECG or EKG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest X-ray, computed tomography (CT scan) of the chest, echocardiography, electrophysiological studies, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, and radionuclide angiography. Please see these procedures for additional information.
Reasons for the procedure
Some reasons for which an ultrafast CT may be performed include, but are not limited to, the following:
- to assess the condition of the coronary arteries
- to assess heart tissue damage after a heart attack (also called myocardial infarction, or MI)
- to assess the patency (openness) of coronary artery bypass grafts
Ultrafast CT is used primarily for the diagnosis of coronary artery disease, particularly in persons who have no symptoms of the disease but who have significant risk factors for the disease. Ultrafast CT should not be considered a substitute for cardiac catheterization. Computed tomography measurement of coronary calcium is not considered relevant in patients who have already had a heart attack or undergone coronary bypass surgery or coronary angioplasty.
There may be other reasons for your physician to recommend an ultrafast CT.
Risks of the procedure
You may want to ask your physician about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your physician. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.
If you are pregnant or suspect that you may be pregnant, you should notify your physician. Radiation exposure during pregnancy may lead to birth defects.
There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.