What is computed tomography?

Computed tomography, commonly known as a CT scan, uses X-rays and computers to produce images of a cross-section of the body. The patient must lie as still as possible as the table moves through the large, donut-shaped scanning device. Movement could blur the images produced by the scanner.

Before the test

Please be aware that correct preparation is very important for the test to be performed properly.

  • If intravenous contrast material is required for your CT scan, you might be instructed to have a blood test before the CT scan appointment. The purpose of the blood test is to assure your doctor that the appropriate contrast agents will be used for an accurate diagnosis. Failure to obtain the blood test might delay your CT scan appointment.
  • Drink only clear liquids after midnight the night before your scan. Clear liquids include clear broth, tea, strained fruit juices, strained vegetable soup, black coffee, plain gelatin, tomato juice, and ginger ale.

On the day of the test

  • Please plan to arrive 15 minutes before your scheduled appointment time. This will help ensure that your CT scan can be completed on schedule.
  • Take nothing by mouth for four hours immediately before your scan.
  • If you are instructed to drink a special solution ("oral preparation") to prepare for your scan, you will receive the solution and instructions. Please follow the instructions carefully.
  • Continue taking your medicines as usual. Consult your doctor if you have questions.
  • You might be asked to change into a hospital gown because snaps and zippers in street clothes can interfere with the scan. You also might be asked to remove your watch or any jewelry.
  • Please do not bring valuables such as jewelry or credit cards.
  • Please allow one hour for your CT scan. Most scans take from 15 to 60 minutes.
  • The test is performed, and the results are reviewed by registered and licensed technologists and board-certified radiologists.

During the test

  • Depending on the type of scan you need, a contrast material might be injected intravenously (into your vein) so the radiologist can see the body structures on the CT image.

After the contrast agent is injected, you might feel flushed, or you might have a metallic taste in your mouth. These are common reactions. If you experience shortness of breath or any unusual symptoms, please tell the technologist.

  • The technologist will help you lie in the correct position on the examining table. The table will then automatically move into place for imaging. It is very important that you lie as still as possible during the entire procedure. Movement could blur the images. You might be asked to hold your breath briefly at intervals when the X-ray images are taken.

After the test

Generally, you can resume your usual activities and normal diet immediately.

The results of your CT scan should be available to your doctor within 24 hours after the test, Monday through Friday. Your doctor will discuss the results with you.


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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 1/14/2014...#4808