What is CT?

The CT scan, or Computed Tomography scan, is an advanced diagnostic test that uses X-rays, a special scanner and a computer to produce detailed images of a specific area of your body.

These images, when studied in sequence, can give your provider a 3-D view of your body.

The radiation dose is much higher than typical x-rays, but CT often provides much greater information and clarity.  

In some cases, CT scan is preferred over an MRI, as it can assess the anatomy in smaller “slices” and can better evaluate some bone and joint conditions. 

How does CT work?

The scanner is made up of a ring containing an X-ray tube and detectors.

The part of your body your provider wants the radiologist to see will be placed within the ring and the X-ray tube rotates around you.

With each rotation the tube sends X-rays and the receptors measure the amount of X-rays absorbed.

The computer then transforms these measurements into a visual image. This image is viewed on a computer screen during the exam and later converted to digital media for the radiologist and your provider to study.

How to prepare for your CT

Different types of CT tests have different preparation instructions. Your provider and/or our imaging center will provide you with specific instructions for your particular scan prior to your appointment. For any type of CT exam please remember to:

  • Wear comfortable, loose fitting clothing. If needed we will provide you with a hospital gown or scrubs to change into for your exam.
  • Tell your provider and the technologist if you are allergic to, or have ever had a reaction to, iodine contrast
  • Tell your provider and technologist about any medications you are taking
  • Tell your provider and technologist if you are pregnant, think you might be, or are breastfeeding
  • You may be asked to remove any hairpins or jewelry that may interfere with your CT scan.

What to expect on the day of your exam

  • Please plan to be in our imaging center for at least 30 minutes on the day of your exam.
  • After you check in at the front desk, the technologist will talk with you prior to your exam and ask you questions about your overall health history, current medications and prior imaging studies.
  • The technologist will then position you on the CT table, ensuring you are as comfortable as possible. You will be able to communicate with the technologist during the entire exam through a patient intercom system.
  • You will need to remain as relaxed and still as possible during your exam to make sure the technologist is able to get the clearest images possible.
  • You may also be asked to hold your breath for short periods of time as images are acquired. The radiologist will review your exam and the results will be sent to your provider for review.

What is contrast?

Some CT exams require a contrast agent to be given to the patient before the exam begins. A contrast agent is used to emphasize specific parts of the body such as vessels, organs and tissues, so they are easier for the radiologist to see.

There are different types of contrast agents which, depending on the type of exam, may be injected intravenously, delivered rectally, or you may be asked to take it orally over a period of time.

At Radia, contrast is used in two different ways:

Oral Contrast – The oral contrast Radia provides comes bottled and pre-mixed in a choice of flavors. Oral contrast is considered to be quite safe and will pass out of the system within a day. Minor cramping or constipation are known possible side effects, but many people experience no discomfort from taking it.

Oral contrast, when mixed with water, may also be delivered rectally in order to maximize the amount of the body that can be seen.  If your exam requires oral contrast, you will be asked to arrive at Radia 90 minutes before your exam to begin taking the contrast orally.

IV Contrast – The IV contrast Radia uses is an iodine-based agent. The most common effects of IV contrast include a "warm, tingly" feeling at the injection site, and a metallic taste in the back of the mouth. Both of these are normal responses to the contrast agent.

Iodine is considered to be safe delivered intravenously, but some people experience an allergic reaction to the material. If you have experienced an allergic reaction to IV contrast in the past please notify your physician so alternatives can be discussed. If your exam requires iodinated IV contrast, you will be asked to sign a consent form which explains the need for contrast, the techniques, the alternatives, and the risks. 

If you have specific questions concerning contrast, please contact your local Radia imaging center and ask to speak to a CT technologist.

For more general information on contrast agents, visit American College of Radiology (ACR) - Contrast Information