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CT Scanning

Basic Facts

  • CT scanning is a diagnostic test that uses x rays and computers to obtain cross-sectional views of internal body structures.
  • Physicians use CT scans to evaluate the structure and function of the heart, as well as to diagnose pericardial disease and diseases of the aorta.
  • Recent advances in CT scanning, including electron-beam and ultrafast scans, have made it easier for physicians to evaluate calcium deposits in the coronary arteries that could be signs of atherosclerosis and coronary heart disease.
In CT scan, a rotating series of X-ray images are taken.
In CT scan, a rotating series of X-ray images are taken.
Computerized axial tomographic scan, also known as CAT scan or CT scan, is a painless test that uses x rays and computers to produce detailed cross-sectional images or slices of the chest, including the heart's chambers and large vessels.

CT scans are used to detect the following conditions:
  • Aortic diseases;
  • Pericardial disease;
  • Congenital heart disease;
  • Cardiac masses and tumors; and
  • Pulmonary embolism.
In addition, high-speed CT scans may be useful in evaluating calcium deposits in the coronary arteries. These deposits may indicate the presence of atherosclerosis, a narrowing or hardening of the arteries.


Typically, patients are asked to avoid solid foods for about 4 hours before the procedure, but they can have clear liquids, such as juice or clear broth. Being hydrated before the test can reduce the likelihood of kidney failure, a potential complication from contrast dye.

Before the test, the patient changes into a hospital gown and removes any jewelry or other objects that may interfere with x rays.


Because CT scanning uses x rays, it exposes the body to radiation. These radiation doses are small, but they can damage cells, which can increase a person's risk for cancer.

Patients that may be unsuited for a CT scan include patients who:
  • Are pregnant (fetuses are vulnerable to x ray radiation);
  • Have an allergy to contrast dye (rare);
  • Have unstable vital signs; or
  • Are claustrophobic.
Women who are nursing should tell the physician if contrast medium (dye) will be used. Some physicians recommend that patients stop nursing for 24 hours after having a CT scan that uses contrast.


A CT scan is usually administered in a hospital or an outpatient facility.

Frequently, a contrast medium or dye is injected to show blood vessels and other structures. The injection may sting slightly, cause a momentary feeling of being warm or flushed, and leave a metallic taste in the patient's mouth.

The CT scanner is a large, square machine with a hole in the center, resembling a donut. Inside the machine, an x ray tube is mounted on a frame, which moves around the patient's body to create the images. The patient will be asked to lie down on his or her back on a narrow table that slides back and forth as well as up and down within the hole. Each time the scanner completes one 360-degree rotation, one thin section or slice of the image is taken and the patient's body is advanced slightly to take another image. These individual sections or slices are reassembled via computer to create a two-dimensional image.

There should not be any unusual sensations during the scanning. Because excessive movement during the scanning may cause blurred images, the patient will be asked to hold his or her breath and stay quite still while each scan is taken. Patients who have difficulty lying still or feel anxious or claustrophobic may be given a sedative.

A CT scan usually lasts 10 to 30 minutes, but some of the newest high-speed spiral or helical scanners can complete an exam in as little as 30 seconds.


Patients resume normal activities and diet immediately following CT scanning. Patients who have been given a sedative, however, must arrange for a ride home.


Patients having CT scans are at risk for the following complications:
  • Allergic reaction to the contrast dye; and
  • Acute kidney failure from the dye injection.
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