An ultrafast computed tomography (CT) scan is an imaging test that uses X-rays and a computer to look at your child's heart. The scan takes pictures very quickly. It gives the doctor many details about your child's heart that other imaging tests can't.

Standard X-rays use a small amount of radiation to create images of bones and organs. These X-rays are useful to help diagnose illness. But many details about internal organs and other structures can't be seen.

With a CT scan, the X-rays move around the body. This gives many views of the same organ or structure in much greater detail. The X-ray information is sent to a computer. The computer makes a 2-D image that your doctor can look at. I.V. contrast dye may also be used to make details show up better in the scan.

An ultrafast CT scan shows the doctor even more details about the heart's structure and how well it is working. It also can be done in much less time than a regular CT scan.

A child may need an ultrafast CT scan to check for:

• Problems with certain arteries and veins.
• Heart damage.
• Heart defects.

Your child's doctor may have other reasons to order an ultrafast CT scan.

Risks include:

• Radiation exposure from X-rays. But the amount of radiation exposure from a CT scan is relatively low.
• Reaction to sedative or anesthesia, such as headaches, shivering, and vomiting.
• Allergic reaction to contrast dye, such as hives, itching, or wheezing.
• In rare cases, kidney damage from I.V. contrast dye.

You can help your child by preparing them in advance. How you do this depends on your child's age and needs. Many hospitals have people trained in helping children cope with their medical care or hospital experience. These people are often called child life specialists. Check with your child's doctor to see if child life programs or other similar services are available for your child.

Here are things you can do to help your child prepare:

• Use short and simple terms to describe the test to your child and why it's being done. Younger children tend to have a short attention span, so do this just before the test. Older children can be given more time to understand the test in advance.
• Tell your child what to expect in the hospital during the test. For instance, you could talk about who will be giving them the test and what the hospital room will look like.
• Make sure your child understands which body parts will be involved in the test.
• As best you can, describe how the test will feel. For instance, if your child is awake during the test, they may feel some discomfort or pressure when the needle is inserted. Reassure your child that this discomfort won't last long.
• Allow your child to ask questions and answer these questions truthfully. Your child may feel nervous or afraid. They may even cry. Let your child know that you'll be nearby during the test.
• Use play when telling your child about the test, if appropriate. With younger children, this can involve role-playing with a child's favorite toy or object. With older children, it may help to read books or show pictures of what happens during the test.

Also make sure to:

• Follow all directions given by the doctor to prepare your child for the test.
• See that your child does not eat or drink for a certain number of hours before the test, if contrast dye will be used during the test.

And tell your child's doctor if your child:

• Has ever had a reaction to any contrast dye.
• Is allergic to iodine.
• Is pregnant or may be pregnant.

The test takes about 30 to 60 minutes. Some may take longer. You may be able to stay with your child in the CT room. Or you may be asked to wait in another area during the test.

A CT scan is done by a radiology technologist. A radiologist is on call in case of problems. This is a health care provider trained to use CT or other imaging methods to test or treat patients.

During the test:

1. Your child lies on a narrow table that slides into the CT scanner.
2. Your child will need to lie still during the scan. Movement affects the quality of the images and can even need a repeat scan. Your child may be restrained or given medicine to relax (sedative) or sleep (anesthesia). The sedative is taken by mouth or given through an I.V. A nurse helps with this process.
3. The technologist is nearby and watches your child through a window. If your child is awake, they can speak to and hear the technologist through a speaker inside the scanner.
4. Contrast dye may be used to improve image results. Your child is given contrast dye by mouth or an I.V. line.
5. Once the scan begins, your child will need to lie very still at all times. At times, they will be told to hold their breath for a few seconds.

Once the test is finished, the table will slide out of the scanner. A child who received medicine to relax or sleep will be watched until the medicine wears off and they are awake again. If an I.V. was inserted, it will be taken out after the test is over and your child is awake.

If no sedation was used, your child can go back to normal activities and diet right away, unless the doctor says otherwise. Contrast dye should pass through your child's body in about 24 hours. Your child may need to drink more water during this time.

If your child had sedation, they may feel sleepy for a while. This should go away in a few hours or a day.

Your child's doctor will talk with you about the results of the CT scan and let you know if other tests are needed.

Before you agree to the test or procedure for your child make sure you know:

• The name of the test or procedure.
• The reason your child is having the test or procedure.
• What results to expect and what they mean.
• The risks and benefits of the test or procedure.
• When and where your child is to have the test or procedure.
• Who will do the procedure and what that person's qualifications are.
• What would happen if your child did not have the test or procedure.
• Any alternative tests or procedures to think about.
• When and how you will get the results.
• Who to call after the test or procedure if you have questions or your child has problems.
• How much you will have to pay for the test or procedure.