Computed Tomography (CT) Scan

Last Updated 11/02/2020

Authors:Samantha D’Annunzio, MD; Melissa Lesko, DO, BA

About Computed Tomography (CT) Scans

Computed tomography, more commonly called a cat scan or CT scan, is an imaging test. A CT scan uses a series of images taken from different angles to create detailed pictures of the inside of your body. A computer collects the pictures and puts them in order for your health care provider.

Compared with traditional X-rays, CT scans create two-dimensional images. These images give providers more information about your bones and organs. Many times, providers ask for CT scans because they notice something unusual in an X-ray. Although the CT scan cannot give a definitive diagnosis, it is a helpful tool to evaluate lung diseases and conditions such as pneumonia, cancer, blood clots, or damage caused by smoking.

What to expect

You may be given specific instructions prior to the scan, such as instructions about eating or drinking. If your CT scan requires contrast, you may be told not to eat anything at least 2 hours prior to your scan. Be sure to follow any instructions you receive.

Before your scan, alert your provider or technician if you have kidney issues or allergies to medications or food, particularly iodine. Also, tell your provider and technician if you think you may be pregnant.

Depending on where on your body the scan is being done, you may need to remove some of your clothing and wear a gown. You take off your glasses, and you remove any metal objects from your body, such as jewelry.

If your provider ordered a CT scan with contrast, you will receive an intravenous (IV) injection. You may feel a warm feeling throughout your body during this injection: This sensation will go away quickly.

At your CT scan appointment, you lie flat on the CT scan table. The table then moves quickly through a donut-shaped device called a scanner. You will be asked to remain still and hold your breath for a few seconds. A CT scan may seem similar to a magnetic resonance imaging (MRI) scan, but it’s slightly different. A CT scanner is open and less noisy than an MRI machine, it uses radiation rather than magnets, and a CT scan takes much less time.

After your scan

After your CT scan, you can return to your regular activities.

Understanding the results

The results of a CT scan are usually ready within a few days. You will schedule a follow-up appointment or call with your provider to talk about your results. During this appointment or call, your provider will discuss the results and recommend next steps, if any. You may need to repeat the CT scan, or you provider may schedule additional tests or a procedure, such as a biopsy. You can always ask for a copy of your CT scan images for your own records.

If you have questions about the results of your scan, ask your provider.

What are the risks?

A CT scan is a fast test, and the open equipment is easier for people with claustrophobia. The most significant risk of CT scans is radiation exposure. However, the benefits of the information the scan providers are important. If you’re concerned about the risk of radiation, discuss this risk with your provider.

Allergy information

If you will have a CT scan with contrast, tell your provider and technician if you have an allergy to iodine or IV contrast. You may need to take medications before the scan.

CT scans with contrast can affect your kidney function, so your provider will check the results of a blood test prior to scheduling the test for you.