Resources and information for parents of children with cancer . . . by parents of children with cancer.

this page last modified

CT Scans 

Note: This section has health/medical information. It was not written by a health care professional. The main medical reference is "Medicine's New Vision" by Howard Sochurek (1988).

A Diagnostic Procedure

The Technical Facts

"CT" stands for computed tomography. It is also called "CAT" for computerized axial tomography; both names indicate the same diagnostic test.

CT is a complex, computer enhanced procedure for obtaining X-ray images of the body. The CT machine resembles a huge donut standing on its edge. The diameter of the "donut" is about 5 feet, and the hole is about 40 inches. The person being scanned rests on a movable table and is moved conveyor-belt style into the machine. Since the machine produces X-rays, the technician sits in a separate room by the computer.

An X-ray source spins around the donut of the machine, sending out a fan-shaped beam, doing one circumference in less than 2 seconds. After passing though the body, they reach a detector on the opposite side. During their travel to the detector, they will be absorbed more or less depending on the type of tissue through which they pass. The more they are absorbed, the fewer the X-rays that reach the detector, and the lighter the shade of gray. The less they are absorbed, the more numerous the X-rays that reach the detector, and the darker the shade of gray.

(From "Medicine's New Vision" by Howard Sochurek: used with the permission of the author.)

There are about 1,000 detectors, each of which is a solid state crystal chip coated with cesium iodide, enabling the signal each receives to be sent to a computer. The computer is able to detect over 200 "shades of gray", compared with conventional X-ray images of about 30 shades of gray. The computer takes the images from each pass of the X-ray source around the circumference and puts them together as cross-sectional slices of the body. The number of cross-sections depends on how many scans are needed for the particular diagnosis; generally it takes about 20 minutes for the actual procedure.

CT scans can be manipulated by the computer to give a 3-D picture of the body. CT has been around since the early 1970s; the instruments cost about a million dollars. There are about 30,000 of these instruments in the US, enough so that it usually does not take long to schedule time on one when necessary for diagnostic purposes. Results are usually given within hours of the test. The amount of X-rays to which the person is exposed is about the same an in an annual dental exam.

The scans are done on an out patient basis. The patient wears a hospital gown during the procedure. Sometimes a "contrast dye" is injected into a vein or given orally to enhance the CT image. Usually fasting is not necessary prior to the procedure. The cost (before insurance) varies from $2000-$3000.

The Parent Facts

CT scans usually do not cause any discomfort for adults, even if they have to drink a "contrast" dye. But kids? Well, that can be an entirely different story.

Lying Still

The ability to lie unmoving for the duration of the scan depends both on the age, personality, and state of illness of the child. Plus, the CT scan emits X-rays, so you, the parent, can't just stand there unprotected and hold your child's hand. Parents often can wear a lead apron and stay next to their child. Here are some parents' recounts.

"They used a sedative for her that's in the phenobarb family - I forget the name. Katy wakes up screaming from versed and the sedative they used for her EEG made her hyper instead of sleepy so we had to look for an alternative that wasn't complete general anesthesia."

The Contrast

Most adults will simply drink the contrast dye because they know that they have to. It has a metallic taste, but supposedly is not all that terrible, to an adult. But, kids? We know about our kids and eating/drinking likes and dislikes. How do you explain to a young child that they have to drink something that tastes awful? Sometimes the contrast is administered IV -- one more needle poke for these over-poked kids! The child may also need to fast for several hours before the contrast is given.

There are forms of the contrast that are more palatable, which you can get if your hospital is way ahead of you or if you ask politely (now, cancer parents are always polite, right?).

References: "Medicine's New Vision" by Howard Sochurek, "Nuclear Medicine", by Wendy and Jack Murphy. These are both books which I checked out from the local public library. I searched, and could not find much information on the Internet on CT scans. (3/98)

General Disclaimer

These pages are intended for informational purposes only and are not intended to render medical advice. The information provided on Ped Onc Resource Center should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you suspect your child has a health problem, you should consult your health care provider.

about this site | privacy statement | terms of use | contact