Computed tomography

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Computed tomography (CT) scan, or computerized axial tomography (CAT) scan is a combined series of x-rays taken from various angles to generate cross-sectional images of bones and tissues inside the body. The images are used by medical doctors individually or in 3D to help diagnose and determine internal injuries, blockages, and tumors. It can also help doctors to monitor certain ailments like heart disease and guide them in surgery and radiation therapy.


How the test is performed

Patients are asked to lie down on a narrow bed. Depending on what is studied, some may need to lie on their back, stomach or side. While the patient is inside the scanner, the x-ray beam will rotate around the subject to create the images. Sensors inside the scanner measures the amount of x-ray needed to penetrate the subject being studied.

Keeping still is very important as the slightest movement can create blurred images. There may be times that the technician will ask the patient to hold his breath.

A CT scan will only take a few minutes. The latest scanners can scan the entire body in less than one minute.

How to prepare for the test

Some tests need the use of dyes or contrast to be taken by the patient prior to the test. The purpose of contrast is to highlight certain parts in the body to make clearer images.

Types of contrast delivery:

Patients may be asked to remove their hospital gown and their jewelry plus anything that may interfere with the test.


CT scans are strictly supervised to ensure that the patient gets the lowest possible exposure to x-ray. Radiation is known to potentially cause cancer and other defects. Some patients may experience a burning sensation when iodine (contrast) is delivered intravenously due to allergies.


  • CT scan. Mayo Clinic (Accessed on 25 January 2011)
  • CT Scans. MedlinePlus (Accessed on 25 January 2011)