CT Scans Provide Additional Information

Q:  I've had increasing shortness of breath over the past several months, but my chest x-ray has been normal. Now my doctor has ordered a CAT scan.

What exactly is a CAT scan? Should I be worried?

A:  "CAT" scan stands for "Computerized Axial Tomography," a diagnostic procedure that uses special x-ray equipment to obtain cross-sectional pictures of the body. Tomography uses many small picture "slices" to create a complete three-dimensional image that will represent the inside of your chest.

Nowadays, doctors shorten the abbreviation CAT scan to simply "CT scan." This is partly because CT scans do not only produce "axial" images, or images that are cross-sections of the body, but can also show length-wise slices, or slices on a diagonal.

You need not be worried about the CT scanning procedure. Wearing a gown, you will lie down while the donut-shaped scanner moves over your chest. The scanner is essentially sending x-rays from every angle in the circle around you, and at every level of your chest from your neck to the bottom of your rib cage.

Although CT scans do not cause any pain, lying in one position during the procedure might be slightly uncomfortable for some people. It will take about 15-30 minutes, depending on the exact study ordered.

For most people, the CT scan is performed on an outpatient basis at a hospital or a doctor's office, without a hospital stay.

There are some small risks with CT scanning. First, if your scan involves the use of intravenous "contrast," you will need an intravenous (IV) line in your hand. The contrast is injected in your veins and allows the CT images to more clearly represent areas with blood flow, including the major vessels in the chest.

A small number of patients might be allergic to contrast dye, and could experience mild itching or hives (small bumps on the skin). Rare symptoms indicating a more serious allergic reaction include shortness of breath and swelling of the throat or other parts of the body. People should tell the technologist immediately if they experience any of these symptoms, so they can be treated promptly.

People with kidney problems may need special attention (e.g., IV fluids) to be sure the contrast dye flushes out without hurting the kidneys.

Since CT technology uses x-ray radiation, it cannot be used for patients who are pregnant.

Some people might be concerned about the amount of radiation they receive during a CT scan, but the information gained from a CT scan outweighs the small radiation dose. Not having the procedure can be more risky than having it, especially if any disease is suspected.

Finally, just because your doctor has ordered a CT scan, it doesn't mean he or she thinks you have a serious disease. CT scans are frequently critical to understanding why someone has a symptom like shortness of breath. You'll be glad to have an answer.

Julie L. Mitchell, MD, MS, is an Assistant Professor of Medicine at the Medical College of Wisconsin. She practices at the Froedtert & The Medical College of Wisconsin General Internal Medicine Clinic - East. Her column appears in the Milwaukee Journal-Sentinel.

This article includes information from the National Cancer Institute.