In standard X-rays, a beam of energy is aimed at the body part 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 a computed tomography (CT or CAT) scan, 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 that interprets the X-ray data and displays it in two-dimensional form on a monitor.
A technology called ultrafast CT (computed tomography) has been in use for over a decade 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, while also greatly decreasing the amount of time required for a study.
Ultrafast CT can detect very small amounts of calcium within the heart and the coronary arteries. This calcium has been shown to indicate that lesions which 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 is being used by many doctors as a means to diagnose early coronary artery disease in certain people, especially persons who have no symptoms of the disease.
You may want to ask your doctor 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 types of CT scans and other types of X-rays, so that you can inform your doctor. 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.
Ultrafast CT is currently used primarily for the diagnosis of coronary artery disease, particularly in people 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.
Ultrafast CT is usually performed on an outpatient basis. There is no preparation necessary prior to the procedure. Although each facility may have specific protocols in place, generally an ultrafast CT procedure follows this process:
The patient will lie on the narrow table of the scanner and will be positioned by a staff member.
The patient may be given a call bell to hold in his or her hand so that he or she can notify the staff if he or she needs assistance.
Once the patient is positioned correctly, the table will slide slowly into the scanner.
Once inside the scanner, the staff will give instructions through the speakers. The patient will hear clicking noises as preliminary adjustments are made.
Once the procedure begins, the patient will need to be very still at all times so that movement will not adversely affect the quality of the images.
At intervals, the patient will be instructed to hold his or her breath, or to not breathe, for a few seconds. He or she will then be told when he or she can breathe. The patient should not have to hold his or her breath for longer than a few seconds, so this should not be uncomfortable.
Once the procedure is finished, the table will slide out of the scanner. The patient will be assisted in getting up.
The patient may be asked to wait for a short time while the radiologist reviews the scans to make sure they are clear and complete. If the scans are not sufficient enough to obtain adequate information, additional scanning may be necessary.
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