What is a CT or CAT scan?

Computer-assisted tomography (also known as CAT or CT) scan is a special type of x-ray that provides a more detailed view of organs, blood vessels, bones and soft tissue than regular x-rays. CT scans take multiple images from different angles of the part of the body being scanned. The result is a series of images that looks like “slices,” which can then be reconstructed on a computer to provide a three-dimensional cross-sectional view of the body area that was scanned. These cross-sectional views help your doctor to better diagnose problems such as cancer, heart disease, back problems, blood clots and other disorders.

CT scanner at UIHC

CT scan of the kidneys

What can I expect during a CT scan?

Clothing
Depending on the type of scan you are having, you may be asked to change into a hospital gown. In some cases you may be able to wear your regular clothing, so we encourage you to wear loose-fitting, comfortable clothes. You may also be asked to remove any items that would interfere with the scan, such as jewelry, belt buckles, glasses or dentures.

Administration of Contrast Solution (sometimes referred to as “dye”)
Contrast solution for CT is a non-radioactive substance that makes your internal structures more visible on the scan. There are three ways you might be given a contrast:

• If you are having a scan of the abdominal or pelvic area, you might be asked to drink a contrast solution 1 to 2 hours before the exam. The contrast solution has a sweet fruity flavor, and most patients do not find it too unpleasant to drink.
• If you are having a scan of the bowel, you may be given the contrast solution rectally with an enema.
• Other types of scans may require that you receive contrast through an IV line. The IV is usually administered right before the exam, and you may feel your face flush or have a metallic taste in your mouth as it is being injected. These senations generally last less than a minute, however.

Occasionally patients may experience an allergic reaction to the contrast. Let the technologist know in advance if you have any known allergies to iodine, or if you experience any itching, rash, hives, or any difficulties with breathing or swallowing during the scan.

Scanning
A technologist will help to position you on the examination table. If you require IV contrast, it will be administered at this time. The technologist will step into an adjacent room where the controls for the CT are located. The examination table will then move through the donut-shaped opening of the CT machine (called a “gantry”), and you will hear a whirring sound as the scanning begins. You will need to remain very still. You may also be asked to hold your breath for a few seconds at a time while the machine is scanning. The scan generally takes between 10-15 minutes, but can sometimes last up to 45 minutes.

What should I do to prepare for a CT scan?

Your healthcare provider will give you a list of instructions to follow for your particular exam type. Certain types of exams may require that you not eat for a period prior to the exam. Contact your healthcare provider if you have any questions.

You are advised to wear comfortable, loose-fitting clothing. You may have to sit for awhile in the patient waiting area, so you might want to bring a book to read or music to listen to.

What if I am claustrophobic?

The CT scanner has a short, donut-shaped opening, so most people with claustrophobia do not have difficulty with CT scans. The machine itself does not touch you, nor is it confining. If, however, you are severely claustrophobic, you may discuss the possibility of a mild sedative with your doctor.

Are CT examinations safe?

CT scans expose the patient to a greater dose of radiation than regular x-rays do, although radiation dose will vary according to the size of the body area being scanned, as well as the type of scanner and operation required to perform that scan. The primary risk associated with radiation exposure from a CT scan is the slight possibility that the patient could develop cancer later in life. According to the FDA (http://www.fda.gov/cdrh/ct/risks.html), approximately 1 in 2,000 patients may develop a radiation-induced fatal cancer sometime in their life; whereas, 1 in 5 patients will develop cancer from natural causes. So the risk of developing cancer as a result of exposure to radiation from a CT scan is far less likely than it is for developing cancer from other natural causes.

In cases where the physician feels there is medical need, the benefits of a CT scan far outweighs the risks. For those who don’t exhibit medical need, however, the risks may outweigh the benefits. It is for this reason that University of Iowa Hospitals & Clinics does not perform whole body screening CTs.

When will I get the results of my examination?

Once the technologist has obtained all the images needed, those images will then be sent to one of our staff radiologists. The radiologist will review the scan on a computer and send the results to your physician. Your physician will then discuss the results with you.