Computed Tomography (CT) Scan

Computed tomography (CT), also known as computerized tomography or computed axial tomography (CAT), is a test that uses computers and X-rays to produce detailed images of the inside of the body. For pediatric cancer, CT can be used to help diagnose a tumor, provide information about the stage of a cancer, observe response to treatment, guide procedures such as a biopsy, and help plan radiation treatments.

During a CT scan, multiple images are taken from several different angles, usually in a very short time, as the part of the body (such as the head, chest, abdomen or the entire body) is scanned. The cross-sectional images can be viewed on a computer monitor, printed on film, or transferred to a CD or DVD. They can be reformatted in multiple planes and can produce three-dimensional images.

What can patients expect during a CT scan appointment?

Each pediatric center has its own procedures, but generally a patient can expect the following: 

• Check-in/registration: First, the patient and parent will check in at the registration desk and then wait in the waiting area until the patient’s name is called. It is important to arrive a few minutes early for check-in so that the patient is ready for the scan at the appointment time.
  
• Meeting the CT technologist: When it’s time for the scan, a CT technologist will escort the patient and parent into a special area that houses the CT scanner. A child life specialist may also be there to help explain the process to the patient and answer questions. A parent can usually stay with the patient during the scan but must wear a lead apron to protect from radiation.
  
• Preparing for the scan: If patients are wearing clothing and accessories that contain metal, such as belts, zippers, snaps, buttons, hair accessories, a watch, jewelry, or a non-permanent retainer, they will be asked to remove those items. It is best to wear loose, comfortable clothing that doesn’t contain metal and leave metal accessories at home. Sometimes patients will be asked to wear a hospital gown.

• Contrast agent: Sometimes a contrast agent is needed to make the images even more clear and detailed. These agents are clear liquids that may be swallowed or injected into a vein through an IV. If swallowed, the liquid might smell or taste funny. If given through an IV, it might feel warm as it goes into the vein. 
  
• Length of scan: The scan often takes a few seconds only but may be repeated if IV contrast is given. The entire exam, depending on its complexity, may take 10 to 20 minutes.  
  
• Sedation: Sedation will only be given if the patient needs it to remain still during the scan. It is very important to lie still, so that the images are clear. If the patient moves or talks during the scan, it may blur the image, and the scan will have to be repeated. It can help if the patient pretends to sleep or to be a statue. Older patients may be asked to hold their breath for a moment.
  
• What happens during the scan: The machine is shaped like a large donut with a special bed, also called a table, in the middle. The CT technologist will position the patient on the table. This table can move up and down and back and forth, so the patient is in the correct location for the scan. There will be a pillow for the head and a wide, soft safety belt to help the patient lie still and in the correct position.  In some cases, the technologist may put towels around the patient’s head and a small, soft belt over the forehead to help the patient to stay still. Most pediatric centers allow patients to bring a comfort item, such as a stuffed animal or a blanket. The CT technologist will move to an area close by and will be able to see, hear, and talk to the patient during the procedure.  
  
• What the patient will see and hear: When the scan starts, the patient will see the red lines of the camera, and the CT machine will make loud noise, such as a “clunk” when the scanner starts and a “whir” or “whoosh” as the camera moves around the patient’s body. The camera does not touch the patient, and the patient will not feel anything as the detectors collect the data to produce pictures. Usually the parent can hold the patient’s hand or stand by the patient while scan is occurring. 
  
• After the test: Once the test is over, the technologist will unfasten safety belts and disconnect the IV if one was used. Then the patient may get off the table and leave the area. 
  
• Test results: A physician called a radiologist will evaluate the images and send an official report to the physician who referred the patient for the exam.  
  
• Conference with physician: The doctor will discuss the results of the CT with the patient and family. It may be a day to several days after the CT. 
  
• Follow-up: Follow-up examinations may be necessary. Your doctor will explain the exact reason why another exam is requested. For example, follow-up examinations are sometimes the best way to see if treatment is working. 
  

What should patients and parents do to make sure the appointment goes smoothly?

• Patients should dress in loose, comfortable clothing without metal snaps or zippers. Do not wear a watch, jewelry, or hair accessories with metal. Metal shows up on CT scans and can block what the doctor needs to see. Avoid wearing eyeglasses, particularly for head CT scans. 
  
• Arrive a few minutes before your appointment time to allow time to check in.
  
• Parents should inform caregivers if their child  
  
  • Is allergic to contrast agent or iodine
    
  • Might be pregnant
    
  • Is uncomfortable in small spaces
    
  • Has special behavior needs 
    
  • Has diabetes or kidney problems
    

What are the benefits/ risks of a CT or CAT scan?

Benefits

CT images of internal organs, bones, soft tissue, and blood vessels provide more detailed pictures than traditional X-rays, particularly of soft tissues and blood vessels. The cross-sectional images generated during a CT scan can be reformatted in multiple planes and can produce three-dimensional images. The scans give doctors a wealth of information to help in the diagnosis and treatment of cancer in children.

Risks

CT scans use a small amount of radiation that is adjusted according to the child’s age and size. Most centers have elaborate strategies to reduce the dose of radiation, specifically designed for each child’s individual case. 

Radiation exposure from CT scans affects children differently than adults. Children are more sensitive to radiation because of their growing bodies and the rate at which their cells divide. Also, they have a longer life expectancy than adults, so there is more time for radiation-related side effects, which include the very low risk of cancer, to develop. The lifetime risk of cancer from a single CT is small – about 1 case for every 10,000 scans in children, according to the National Institutes of Health. The risk increases when multiple CTs are performed.

Three key questions that parents can ask health care providers regarding radiation safety:

1. Why is the test needed?
2. Will the results change the treatment decisions?
3. Is there an alternative test that doesn’t involve radiation?

If the CT is medically necessary, experts say the benefits outweigh the small, long-term risk of radiation exposure.

If you have any questions about CT safety, ask your physician.