Computed tomography (CT) a method of body imaging in which a thin x-ray beam rotates around the patient. Small detectors measure the amount of x-rays that make it through the patient or particular area of interest.

A computer analyzes the data to construct a cross-sectional image. These images can be stored, viewed on a monitor, or printed on film. In addition, three-dimensional models of organs can be created by stacking the individual images, or "slices."

You will be asked to lie on a narrow table that slides into the center of the scanner. Depending on the study being performed, you may need to lie on your stomach, back, or side. If contrast dye is to be administered, an IV will be placed in a small vein of a hand or arm.

Much like standard photographic cameras, any motion you make causes blurred images in CT. Therefore, the operator will give you instructions through an intercom on when to hold your breath and not move.

As the exam takes place, the table will advance small intervals through the scanner. Modern "spiral" scanners can perform the exam in one continuous motion. Generally, complete scans will only take a few minutes. However, additional contrast-enhanced or higher-resolution scans will add to the scan time. The newest multidetector scanners can image your entire body, head to toe, in less than 30 seconds.

You may be asked to drink contrast immediately prior to the CT scan, or 4 to 6 hours beforehand. The contrast may be non-reactive, chalky-tasting barium sulfate, which will eventually pass in the stools, or absorbable clear Gastrografin solution. You may also be asked to fast (no solids or liquids) for 4 to 6 hours if contrast dye is to be used.

The CT scanner has a weight limit to prevent damage to its internal mechanisms. Have the health care provider contact the scanner operator if you weigh more than 300 pounds.

Since x-rays have difficulty passing through metal, the patient will be asked to remove jewelry and wear a hospital gown during the study.

The x-rays are painless. The primary discomfort may be from the need to lie still on the table.

If intravenous contrast dye is given, the patient may initially feel a slight burning sensation within the injected arm, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually reside within a few seconds.

CT provides rapid, detailed cross-sectional imaging of the patient which can then be reconstructed into three-dimensional models, as needed. Intravenous contrast enhanced scans allow for evaluation of vascular structures and further evaluation of masses and tumors.

CT is often utilized in the trauma setting to evaluate the brain, chest, and abdomen. As well, CT can be used to guide interventional procedures, such as biopsies and placement of drainage tubes.