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    CT Scan (Computed Tomography)

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    What is a CT Scan (Computed Tomography)?

    A CT scan, also known as a CAT scan, is a test that uses X-rays and a computer to take pictures inside your body (for example, muscles, organs, and bones). This helps your doctor find the cause of your illness. A specially trained person, called a Radiologic Technologist, does a CT scan.


    Note: If you are pregnant, you must tell your doctor and/or the Radiologic Technologist before your CT scan.

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    Before Your CT Scan

    • Your doctor gives you a referral form that tells the Radiology (X-ray) Department what area of your body to scan. Bring this form to your appointment. Before your CT scan, make sure your doctor's office faxes this form to the Radiology Department.


    • The doctor or staff may tell you not to eat for 3 hours before your CT scan. This means no food, liquids, smoking, or chewing gum.
      Note: You may take required medicines with a small amount of water.


    • If you are having an abdominal and/or pelvic CT scan, you may need to arrive one (1) hour before your test. The staff will ask you to drink a liquid, called a contrast. This contrast helps the doctor see the CT scan more clearly. Sometimes, you may need to drink more contrast right before the test.


    • Contrast may also be put in a vein (IV) in your arm. If you have an allergy to IV contrast used in some X-rays, please tell your doctor and/or the Radiology Department before your appointment. If you are receiving IV contrast, it is important to drink 5-6 glasses of water the day before your test.

      Note: If you receive an IV contrast, you may have a warm or hot feeling in your body as the contrast is put in your vein. You may also notice a metallic taste in your mouth. The IV stays in your arm for most of the test.


    • For some tests, contrast may be given in the rectum (by enema).

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    During Your CT Scan

    • The CT scan usually takes 15 minutes or less. This test does not cause discomfort or pain for most people.


    • You are put into the CT scanner, which is a large machine with a hole in the middle (see picture above). Most of the time, you lie on your back with support under your knees. You need to stay very still during the test.

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    After Your CT Scan

    • If you received IV contrast, drink plenty of liquids (6-8 glasses) after your CT scan. The contrast comes out in your urine. It will not change the color of your urine.


    • If you drank liquid contrast, it will come out in your stools. The contrast may soften your stools.

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    Getting Your Test Results

    Usually, the results of your CT scan are given to your primary (regular) doctor 1-2 days after your test.

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    More Ways to Learn

    Visit the RadiologyInfo.orgOpens new window Web site.

    Note: This handout is also available in Chinese, Russian, and Spanish.



    Produced by the Center for Patient and Community Education in association with the Department of Radiology at California Pacific Medical Center. Last updated: 9/06

    Photo by Bill Posner.


    Funded by: A generous donation from the Mr. and Mrs. Arthur A. Ciocca Foundation.

    Note: This information is not meant to replace any information or personal medical advice which you get directly from your doctor(s). If you have any questions about this information, such as the risks or benefits of the treatment listed, please ask your doctor(s).
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