What It Is

A CAT scan of the head (also called a head CT) is a painless test that uses a special X-ray machine to take pictures of a patient's brain, skull, and sinuses, as well as blood vessels in the head.

The doughnut-shaped machine circles the head, taking pictures to provide cross-sections of the brain from various angles. These pictures are sent to a computer that records the images. It also can put them together to form three-dimensional images.

A radiology technician performs the CAT scan (also called a CT scan or a computed axial tomography scan).

Why It's Done

A head CAT scan may be done in order to:

• detect conditions in the brain such as hydrocephalus (too much fluid in the ventricles), swelling, inflammation, bleeding, and signs of injury
• gather information about the presence, location, and size of abscesses, cysts, and tumors
• locate birth defects in the brain and skull
• evaluate the pituitary gland, pineal gland, and sinuses
• look at malformed or injured blood vessels in the head
• find the cause of headaches, weakness, or a change in mental status

Preparation

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

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

If 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

The scan itself generally takes less than 10 minutes. Total time depends on the age of the child, whether contrast solution is given, and whether sedation is needed. Actual exposure time to radiation is much less.

Your child will enter a special room and lie down on his or her back on a table. A pillow and sometimes a soft brace holds the head and neck in place to prevent movement that would result in a blurry image.

If contrast solution is required for the CAT scan, it will be given in the radiology area through an IV (intravenous) line placed in your child's hand or arm. Placing the IV will feel like a quick pinprick, and the solution is painless as it goes into the vein.

Sedation may occasionally be required if your child can't lie still for the scan. Sedation medicines are given through an IV line and help to keep a child comfortable during the CAT scan. Since the scan is brief, other soothing methods are often attempted first.

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 with your child until the test begins and possibly during the test. If you leave the CAT scan room, 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 or in the CAT scan room, you'll be asked to wear a lead apron to protect certain parts of your body.

When the procedure starts, the table moves through the CAT machine. Older children may be asked to hold their breath for a few seconds at a time to prevent blurring of the image.

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 children 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're blurred, 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 specially trained in reading and interpreting X-ray images). The radiologist will send a report to your 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 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. Talk with your doctor if you have any concerns about a possible allergy. 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.

If your child requires sedation, there's a slight chance of slowed breathing due to the medications. If there are any problems with the sedation, the CAT scan staff is prepared to treat them right away.

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 close by. For older kids, be sure to explain the importance of keeping 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 head CAT scan is needed, speak with your doctor. You also can talk to the CAT scan technician before the procedure.

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