What It Is

A chest CAT scan is a painless test that uses a special X-ray machine to take black-and-white pictures of a patient's lungs, heart, blood vessels, airway passages, ribs and lymph nodes.

The doughnut-shaped machine circles your child's body, taking pictures to provide cross-sections of internal organs from various angles. These pictures are sent to a computer that records the images. It can also put them together to form a three-dimensional (3-D) image. A radiology technician does the CAT scan (also called a CT scan or a computed axial tomography scan).

Why It's Done

A chest CAT scan can detect signs of inflammation, infection, injury or disease of the lungs, breathing passages (bronchi), heart, major blood vessels, lymph nodes, and esophagus. A doctor may order a chest CAT scan to identify illnesses related to the lungs and breathing passages, to diagnose birth defects, view a tumor, evaluate blood vessels that feed the heart and lungs, or evaluate the effects of a traumatic injury.

Preparation

Your child may be asked to remove all clothing and accessories and change into a hospital gown because buttons, zippers, clasps, or jewelry might interfere with the image.

Your child may have to avoid eating and drinking for a few hours before the scan so the stomach will be empty. Fasting is required if your child needs to be sedated or will receive a contrast solution, which highlights certain parts of the body so doctors can see more detail in specific areas.

If you suspect that your daughter is pregnant, it's important to tell her technician or doctor because there's a small chance that the radiation from the CAT scan may harm the developing baby. But if the CAT scan is necessary, precautions can be taken to protect the baby.

Procedure

Procedure times vary, from several minutes to 45 minutes. This timing depends on the age of the child, whether contrast solution is given, and whether sedation is needed. The actual exposure time to radiation is much less.

Your child will enter a special room and lie down on a narrow table. A chest CAT scan is performed with your child lying on his or her back, stomach, or side. If contrast solution is required, it may be given through an IV that will be placed in your child's hand or arm. Placing the IV will feel like a quick pinprick, but the solution is painless as it goes into the vein. Or your child may be given oral contrast, which is a special fluid to drink before the procedure. Some kids don't like the taste, but it can be flavored to make it more appealing.

The technician will position your child, then step behind a wall or into an adjoining room to operate the machine, viewing your child through a window. The technician will speak to your child through an intercom. You'll be able to stay in the CAT scan room until the test begins, then you'll join the technician in the outer room or you might be asked to sit in a waiting room. If you stay with the technician, you'll be asked to wear a lead apron to protect certain parts of your body.

Sedation may be required if your child can't lie still for the scan, which is common among infants and young kids. Sedation medicines are given through an IV line and help to keep your child comfortable during the CAT scan. When the procedure begins, the table moves through the CAT machine. Older kids will be asked to hold their breath and stay still for a few seconds at a time to prevent the images from being blurred.

What to Expect

Your child won't feel anything as the CAT scan is taken, but may hear whirring and buzzing as the machine works. The room may feel cool due to air conditioning used to maintain the equipment. Some kids may feel uncomfortable lying still for extended periods.

After the scan is complete, your child will be asked to wait a few minutes so the technician can review the quality of the images. If they are blurred, some parts of the CAT scan may need to be redone. If your child required sedation, it will take a little while for the medicine to wear off.

Getting the Results

The CAT scan images will be looked at by a radiologist (a doctor who is specially trained in reading and interpreting X-ray images). The radiologist will send a report to your child's doctor, who will discuss the results with you and explain what they mean.

Results are usually ready in 1-2 days. If the CAT scan was done on an emergency basis, the results can be made available quickly. In most cases, results can't be given directly to the patient or family at the time of the test.

Risks

In general, CAT scans are very safe, although more radiation is required than in a regular X-ray. Any exposure to radiation poses some risk to the body, but the amount used in an individual CAT scan procedure isn't considered dangerous. It's important to know that radiologists use the minimum amount of radiation required to get the best results.

If your daughter is pregnant, there's a risk of harm to the developing baby, so precautions must be taken. Contrast solutions are generally safe, with a very low incidence of allergic reactions. They may contain iodine, which might cause problems for kids with an iodine or shellfish allergy, and other illnesses. Make sure to tell your doctor about any medication, dye, and food allergies that your child may have. Some patients who are at risk for allergic reaction to the contrast solution may need medications like antihistamines or steroids to minimize the risk of adverse reaction.

Helping Your Child

You can help your child prepare for a CAT scan by explaining the test in simple terms before the procedure. You can describe the room and the equipment that will be used, and reassure your child that you'll be nearby. For older kids, be sure to explain the importance of staying still so the scan can be completed quickly and parts of it don't have to be repeated.

If You Have Questions

If you have questions about why the chest CAT scan is needed, speak with the doctor. You can also talk to the CAT scan technician before the procedure.

Reviewed by: Yamini Durani, MD
Date reviewed: September 2011