Key Points about CT Scans

  • A computerized tomography (CT) scan is an X-ray technique that takes multiple images of your body.
  • The exam should take no longer than an hour.


During the exam, an X-ray machine moves around you, taking images from multiple angles. Using high powered computing technology, these images are separated into individual “slices” so your physician can view dozens of images and make a better diagnosis than regular X-ray images.

Preparing for a CT scan

You may be asked to remove your clothing and wear a hospital gown. You'll need to remove any metal objects, such as jewelry, that might interfere with image results.

Depending on the body part being scanned, some CT scans require you to drink a contrast liquid before the scan or have contrast injected into a vein in your arm during the scan. A contrast medium blocks X-rays and appears white on images, which can help emphasize blood vessels, bowel or other structures. If your test involves a contrast medium, your doctor may ask you to fast for a few hours before the test. You may need to pick up contrast the day before your exam. The person scheduling your exam will let you know when and where to pick up contrast.

If you have a known allergy to the contrast material, your doctor may prescribe medications to reduce the risk of any allergy reaction. Although rare, the contrast medium Involved in a CT scan poses a slight risk of allergic reaction. Most reactions are mild and result in hives or itchiness. For people with asthma who become allergic to the contrast medium, the reaction can be an asthma attack.

Please take your usual medicines before the CT scan. We will review your list of medications prior to your exam and then determine if any changes need to be made.

If you are pregnant, have implanted devices such as pacemaker or infusion pumps, have breast tissue expanders or have religious or cultural concerns, please contact the radiology department before your exam..

Please arrive 15 minutes before your scheduled exam.

Expectations during a CT scan

CT exams are painless, fast and easy.  Though scanning causes no pain, you will have to remain still for several minutes, and there may be some discomfort with the placement of the IV. 

During the CT scan, you lie on a narrow table that slides through the opening of an X-ray machine. You may lie on your back, side or stomach, depending on the area to be scanned. The table can be raised or lowered. Straps and pillows may help you stay in position. During a CT scan of the head, the table may be fitted with a special cradle that holds your head still. 

If your exam involves use of an contrast liquid, you may feel a brief sensation of heat or experience a metallic taste in your mouth. If you receive the contrast medium through an enema — to help highlight your lower gastrointestinal region — you may feel a sense of fullness or cramping.

After the exam you can return to your normal routine. If you were given a contrast medium, your doctor, a nurse or the CT technologist performing the scan may give you special instructions. You may be asked to wait for a short time in the radiology department to ensure that you feel well after the exam. After the scan, you should drink lots of fluids to help your kidneys remove the medium from your body. 

Duration of CT scan

Expect the exam to last no longer than an hour, depending on the preparation needed and whether it includes the use of a contrast medium. The scan itself may take less than a minute on the newest machines. Most scans take just a few minutes to complete.