CT Scan (Computed Tomography)

Author: Courtney Misher, MPH, BS R.T.(T)
Last Reviewed: August 02, 2022

Picture of a CT Scanner

CT scans (CAT scans) are medical tests that take pictures of the inside of your body using x-ray technology. The pictures create cross-sectional images, or slices, of your body. The pictures are combined to create a three-dimensional (3-D) picture.

Why are CT scans used?

CT scans show your internal organs, soft tissues, blood vessels, and bones. CT scans have many uses and common uses related to cancer care are:

  • Finding cancer.
  • Learning more about the cancer (where it is and how big it is).
  • Finding where to do a biopsy.
  • Planning your cancer treatment.
  • Checking during treatment to see if your tumor has changed.
  • See if the treatment worked once the treatment is finished.
  • Checking for new cancer during follow-up care.

How do I prepare for a CT scan?

This depends on the part of the body being scanned. Your provider will tell you how to prepare. These are some things you may need to do:

  • You may need to arrive an hour or two before your scan to do paperwork, meet with providers, or finish any preparation needed for the scan.
  • You may be asked to not eat or drink for many hours before your scan. This is common if you will be getting IV contrast. IV contrast can cause a reaction or upset stomach.
  • You may need to do an enema.
  • You should wear comfortable clothing and shoes that are easy to get on and off. Any items that can be removed should be taken off like a wig, dentures, bra, glasses, jewelry, watch, etc.

Why would I need contrast during my CT scan?

If your provider wants you to have contrast during your scan you may be asked to have a blood test. This allows your provider to check your kidney function. The blood test can usually be done 1-2 weeks before your CT scan.

If the CT scan will look at your stomach or bowel, you may be given oral contrast (contrast that you drink). This is done to be able to see the difference between your bowels and other structures.

If you are receiving intravenous (IV) contrast (contrast that is given through a needle into your vein), it will be given either before or during the test. It does not hurt, but some patients do feel warm or flushed after it is given, and this is normal.

If you have ever had an allergic reaction to contrast, you should tell your provider before the exam. You may be given steroids and Benadryl to prevent a reaction.

How is this test performed?

A CT scan is done while you lie on a flat table. This table moves in and out of the donut-shaped CT scanner. The scanner will move around you taking x-rays from many angles. These x-rays will be put together using computer software to create 3-D images.

You must lie still during the test. You may be asked to hold your breath for short periods of time. The test will take anywhere from 15-60 minutes. You will be by yourself in the room, but a technician will be able to see, hear, and talk to you. The test is not painful, but some people find it hard to lie flat and still. The technician will help you get comfortable.

If you are having the CT scan for radiation therapy planning purposes, then the technician will put you in the position you will be in every day for your treatments. They may make special devices like masks or vac-loc bags to help keep you still and keep you in the same position.

How do I receive the results of my CT scan?

A radiologist, who is a doctor that specializes in looking at different types of images, looks at the scan and creates a report. The report provides detailed information about normal and abnormal findings. Your provider will be able to discuss your results with you.

If your CT scan is for planning purposes only, then your radiation oncologist will use the 3-D images to create your radiation treatment plan.

Centers for Disease Control and Prevention. (2021, October 20). Computed Tomography (CT) scans. Centers for Disease Control and Prevention. Retrieved August 1, 2022, from https://www.cdc.gov/nceh/radiation/ct_scans.html#:~:text=Computed%20tomography%2C%20or%20CT%2C%20scans,%2C%20soft%20tissues%2C%20and%20bones.

Computed Tomography (CT) SCAN. Cancer.Net. (2022, July 15). Retrieved August 1, 2022, from https://www.cancer.net/navigating-cancer-care/diagnosing-cancer/tests-and-procedures/computed-tomography-ct-scan

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