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What is a CT scan?

CT Scan - 460x261

A CT scan is an imaging test that uses X-rays and a computer to take cross-sectional pictures of the body. A CT scan, also called a CAT (computed axial tomography) scan, makes layered images of an entire body area. The images are similar to slices of a loaf of bread. CT scans are more detailed than regular X-rays They help doctors diagnose and treat many diseases, disorders and conditions. 

A CT scan is a painless, noninvasive medical test. It makes images of any organ or body part. A CT scan is only one method of diagnosing and monitoring many diseases, disorders and conditions. Discuss all your diagnostic and monitoring options with your doctor to understand which options are best for you.

Types of CT scans

Standard CT scans can make pictures of almost any body structure using only the CT scan machine. Your doctor may add a contrast agent or dye or use specialized CT scan machines and techniques to make clearer or more detailed images. Specialized CT scans include:

  • Cardiac CT makes detailed images of the heart and often involves injecting a contrast dye into a vein.

  • Coronary calcium scan looks for calcium deposits in the coronary (heart) arteries. A coronary calcium scan uses medication to slow your heart and an EKG machine to record your heart’s electrical activity during the scan.

  • CT angiography makes detailed images of blood vessels and tissues by injecting a dye through a small tube (catheter) inserted into a vein.

  • CT enterography makes detailed pictures of the small intestine using a contrast dye that you drink.

  • CT colonography (virtual colonoscopy) makes detailed pictures of the inside of the large intestine. It involves pumping carbon dioxide gas through a tube in the rectum to expand the large intestine for better viewing.

  • Multislice CT or multidetector CT makes thinner imaging slices in a shorter period than a traditional CT scan. This creates images with more detail.

  • SPECT (single-photon emission computed tomography) shows the function of organs. A SPECT scan is a type of nuclear imaging test that uses a radioactive substance and a special camera combined with CT scanning to create 3-D pictures.

  • PET/CT (positron emission tomography/computed tomography) is used to diagnose or determine the severity of many diseases, such as cancer. PET/CT is a type of nuclear imaging test that makes images using a radioactive substance and a special camera combined with CT to create detailed pictures.

Medical Reviewers: William C. Lloyd III, MD, FACS Last Review Date: Sep 10, 2016

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View Sources

Medical References

  1. Cardiac CT for Calcium Scoring. Radiological Society of North America.
  2. Computed Tomography (CT): Questions and Answers. National Cancer Institute.
  3. CT Angiography. Radiological Society of North America.
  4. CT – Body. American College of Radiology.
  5. CT Colonography. American College of Radiology.
  6. CT Scans. United States Environmental Agency.
  7. Positron Emission Tomography - Computed Tomography (PET/CT). Radiological Society of North America.
  8. What is Computed Tomography? U.S. Food and Drug Administration.

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