Computed tomography (CT) Scan

Also known as: CAT scan

What is a computerized tomography or computerized axial tomography (CT or CAT) scan?

A CT or CAT scan is mostly used to examine the head, chest, abdomen, spine and pelvis with a cross-sectional view where the images appear as “slices” of the body. During a CT scan, a thin beam of X-rays circle the body for a detailed 360-degree view.

Neurological CT scans are used to view the brain and spine. They can detect bone and vascular irregularities, certain brain tumors and cysts, herniated discs, epilepsy, encephalitis, spinal stenosis (narrowing of the spinal canal), a blood clot or intracranial bleeding in patients with stroke, brain damage from head injury, and other disorders. Many neurological disorders share certain characteristics and a CT scan can aid in proper diagnosis by differentiating the area of the brain affected by the disorder.

How to prepare for a CT scan

For a head, chest, abdomen or pelvic scan, you'll need to fast four hours before the exam. Be sure to let the technologist know if you are or might be pregnant.

How the procedure is performed

After the technologist explains the procedure to you, you'll be gently positioned on the scan table and moved into the scanner, which is a small air-conditioned chamber shaped like an upright doughnut. It's important to remain completely still during the exam. The technologist is in constant communication with you and can see you at all times. You'll hear the humming of the scanner and may feel the table move slightly in preparation for the next scan. Most scans take only a few seconds and the entire process takes about 30 minutes.

Some CT scans require the use of a contrast or dye which highlights certain body tissues and structures. For head and chest exams, the contrast is given through an IV. For abdomen or pelvic exams, the contrast is given by mouth and through an IV. If oral contrast is needed, you'll be given the dye shortly before the exam.

Radiation safety, contrast agents

The X-rays used in a CT exam involve a small dose of radiation. Oral and/or intravenous contrast agents may be used, depending on the type of exam. These contrast agents are generally safe, but, like all medications, side effects can occur.

A small percentage of patients are allergic to the intravenous agent. Allergic reactions are usually mild (itching, flushing) but occasionally may be severe. If you've had allergic reactions to contrast agents before, or if you have asthma or multiple allergies, you may be at a higher risk for a reaction. Let your doctor know if you have any of these conditions when scheduling your exam so that an alternative, non-allergenic contrast agent may be used. Anyone may receive the alternate agent, but the additional cost may not be covered by your insurance.

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