Radiology testing instructions for CT Scan can be accessed for printing by clicking here.

What is a CT Scan?
CT (computed tomography), sometimes called CAT scan, uses special x-ray equipment to obtain image data from different angles around the body and then uses computer processing of the information to show a cross-section of body tissues and organs.

CT imaging is particularly useful because it can show several types of tissue—lung, bone, soft tissue and blood vessels—with great clarity. Using specialized equipment and expertise to create and interpret CT scans of the body, radiologists can more easily diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders. Because it provides detailed, cross-sectional views of all types of tissue, CT is one of the best tools for studying the chest and abdomen.

How should I prepare for the CAT scan?
You should wear comfortable, loose-fitting clothing for your CT exam. Metal objects can affect the image, so avoid clothing with zippers and snaps. You may also be asked to remove hairpins, jewelry, eyeglasses, hearing aids and any removable dental work, depending on the part of the body that is being scanned. You may be asked not to eat or drink anything for one or more hours before the exam. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.

What does the equipment look like?
The CT scanner is a large, square machine with a hole in the center. The patient lies still on a table that can move up or down and slide into and out from the center of the hole. Within the machine an x-ray tube on a rotating gantry moves around the patient's body to produce the images, making clicking and whirring noises as the table moves. How is the CAT scan performed?

During a CT scan, you lie on a table inside a doughnut-shaped machine called a gantry. An X-ray tube inside the machine rotates around your body and sends small doses of radiation through it at various angles. As X-rays pass through your body, different tissues absorb different amounts. Detectors inside the gantry measure the radiation leaving your body and convert the radiation into electrical signals. A computer gathers these signals and assigns them a color ranging from black to white depending on signal intensity. The computer then assembles the images and displays them on a computer monitor.

The technologist begins by positioning the patient on the CT table. The patient's body may be supported by pillows to help hold it still and in the proper position during the scan. As the study proceeds, the table will move slowly into the CT scanner. Depending on the area of the body being examined, the increments of movement may be so small that they are almost undetectable or large enough that the patient feels the sensation of motion.

A CT examination often requires the use of different contrast materials to enhance the visibility of certain tissues or blood vessels. The contrast material may be swallowed, injected through an IV directly into the blood stream or administered by enema, depending on the type of examination. Before administering the contrast material, the radiologist or technologist may ask whether the patient has any allergies, especially to medications or iodine, and whether the patient has a history of diabetes, asthma, a heart condition, kidney problems or thyroid conditions. These conditions may indicate a higher risk of reaction to the contrast material or potential problems eliminating the material from the patient's system after the exam.

A CT examination usually takes five minutes to half an hour. When the exam is over the patient may be asked to wait until the images are examined to determine if more images are needed.

If your infant or toddler is having the test, the doctor may give your child a sedative to keep him or her calm and still. Movement blurs the images and may lead to incorrect results. Ask your doctor how to prepare your child.

What will I experience during the procedure?
CT scanning causes no pain, and today’s faster scanners reduce the need to lie still for any length of time. For different parts of the body the patient preparation will be different. You may be asked to swallow a contrast material, a liquid that allows the radiologist to better see the stomach, small bowel and colon. Some patients find the taste of the contrast material mildly unpleasant but most can easily tolerate it. Your exam may require the administration of the material by enema if the colon is the focus of the study. You will experience a sense of abdominal fullness and may feel an increasing need to expel the liquid. Be patient; the mild discomfort will not last long.

A contrast material is commonly injected into a vein to better define the blood vessels and kidneys and to accentuate the appearance between normal and abnormal tissue in organs like the liver and spleen. Some people report feeling a flush of heat and sometimes a metallic taste in the back of the mouth. These sensations usually disappear within a minute or two. Some people experience a mild itching sensation. If it persists or is accompanied by hives (small bumps on the skin), the itch can be treated easily with medication. In very rare cases, a patient may become short of breath or experience swelling in the throat or other parts of the body. These can be indications of a more serious reaction to the contrast material that should be treated promptly, so tell the technologist immediately if you experience these symptoms. Fortunately, with the safety of the newest contrast materials, these adverse effects are very rare.

You will be alone in the room during the scan; however, the technologist can see, hear and speak with you at all times. For pediatric patients, a parent may be allowed in the room with the patient to alleviate fear but will be required to wear a lead apron to prevent radiation exposure.

Who interprets the results and how do I get them?
A radiologist, who is a physician experienced in CT and other radiology examinations, will analyze the images and send a signed report with his or her interpretation to the patient's personal physician. The personal physician's office will inform the patient on how to obtain their results.

What are the benefits vs. risks?

Benefits

• Unlike other imaging methods, CT scanning offers detailed views of many types of tissue including the lungs, bones, soft tissues and blood vessels.
• CT scanning is painless, noninvasive and accurate.
• CT examinations are fast and simple. For example, in trauma cases they can reveal internal injuries and bleeding quickly enough to help save lives.
• Diagnosis made with the assistance of CT may eliminate the need for invasive exploratory surgery and surgical biopsy.
• CT scanning can identify normal and abnormal structures, making it a useful tool to guide radiotherapy, needle biopsies and other minimally invasive procedures.

Risks

• CT does involve exposure to radiation in the form of x-rays, but the benefit of an accurate diagnosis far outweighs the risk. The effective radiation dose from this procedure is about 10 mSv, which is about the same as the average person receives from background radiation in three years.
• Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
• Nursing mothers should wait 24 hours after contrast injection before resuming breast feeding.
• The risk of serious allergic reaction to iodine-containing contrast material is rare, and radiology departments are well equipped to deal with them.