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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.
- "Kathy was terrified (big huge panic is a better description) during both her CT scan and her MRI. The noise (although a CT scan is much quieter than an MRI) scared her ... all noises scare my children."
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 first CT Eric had was on the day he was diagnosed. They told me that the technicians could get EJ to lay still -- I told them it was impossible. Anyway, they were so very close to doing it, but then Eric panicked, so they sedated him. He's been sedated for every MRI and CT since then. After he started using morphine pretty regularly, we had to use anesthesia instead of sedation."
- "I have always been there with Sally (wearing a lead apron) - I've been able to hold her hand or foot and talk to her. It doesn't take very long - only a few minutes and she has managed fine. The noises can be a little overwhelming sometimes but Sally was ok with it all as long as we were there. Also in both places Sally has had a CT the technician was able to speak to her over a microphone and that seemed to help."
- "Linda, unfortunately is very familiar with CT scans. At the very beginning, when she was 3, they would try to give her something to sedate her, of course it wouldn't. So we looked for ways to get her to lie still. The way we accomplished this was by me standing next to her and holding her hand. The parent must wear a shield in order to do this. The CT scanner at Riley does not make that much noise and they just got a new one that looks like a donut with a hole in it that moves around her so she doesn't have to change positions. Anyway, they had a tape player and I would always bring one of her favorite tapes and set the tape player right next to her during the whole thing. Also, they would let her have her blankie and baby with her. They were very accomodating."
- "I always stay in the room with Tiffany and wear the lead apron. It's comforting for her to know that I am there. She was nine when she started and hasn't really had any problems lying still. Before she goes we usually discuss visualization and I encourage her to use that quiet, still time to take a mental journey and tell me about it when she is done. She has a wonderful imagination and sometimes really gets into it. Other times when she wasn't feeling well, either physically or emotionally she would pretty much just tell me to "bug off"."
- "Mary wanted to be a big girl and go in there herself. She didn't seem to mind the scan at all (other than the poke) and came out of the room just smiling away (the hospital gave her a stuffed animal for her trouble!)."
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?).
- "No problems with the contrast, Sandy said it felt cold and she got a funny taste in her mouth. Of course, the needle poke was not fun!"
- "The dye didn't cause any problems for her other than it is just one more "poke" that she absolutely did not want. (The hospital had not told us ahead of time that Pooh was going to be "poked" so she wasn't at all prepared.)"
- "The one time I remember him getting oral contrast it had to be administered via an NG tube (again, I told them he wouldn't drink it!). The other times they just used IV contrast for his head/brain."
- "When Ricky had it done, he was in the hospital for vomiting and running a high fever. They tried to make him drink 4 cups of contrast. Yes, you read that right. He threw up after the first cup. They took him down for the head one, and wouldn't do the bowel one without 4 cups of contrast. Well, they sent him back up, got him back into his bed, and then the docs said that they would do it without all the contrast. So they had to take him back down, and the stupid B*&$# put the contrast through the central line!!! I was livid! She knew it all the time. (The real kicker is that when they did it, the tiny amount that had drunk WAS ENOUGH!!!!) The next time he needed contrast for the second scan, they wanted to put an NG tube down his nose and pump the contrast in. I told the intern, "I absolutely DO NOT give permission for you to put a tube down his nose. He only needs to drink one cup." She checked with the doctor, and I was right. I told my mom-in-law who was with him at the time to only have him drink a tiny bit, and toss the rest, but she is good, and made him drink it all. From now on, I will just lie, and say he drank it all..."
- "2 months ago, with yet another bout of pancreatitis, Bobby was forced to drink the contrast (2 20-oz cups), although NPO for everything else and very nauseous. Needless to say, he spewed all over that machine. He can't stand the IV contrast either, it usually causes a brief "wave" of intense nausea."
- "For Linda, now it is no big deal at all, of course she hates the IV they have to put in to inject the dye. But that is the worst part."
- "We had the exact same problem with Micky. The stuff was called E-Z-Scan and it was a thick, chalky, white goop. I tasted it. Awful. I never made Micky drink all of it. I couldn't be that hypocritical."
- "Tiffany had her first CT scans as an inpatient at the hospital where she had her first surgery. They had her drink gatorade with the contrast. After that she was going to a different hospital for treatment and had to have all her further scans done there. The first opt. CT they gave my DH barium for her to drink. I didn't think it was right but when I called there they told me that was what they used. YUCK! She drank about 1/4 th of what she needed to drink and couldn't drink any more. When we arrived I told them that she was gagging on it. They weren't too compassionate. I felt so bad for her because I had kept trying to get her to drink it. Later they said next time we had to go down to the pharmacy to get the clear contrast to mix with the gatorade. The onc. office had told us to pick it up in the radiology dept., but all they kept there was the barium. The next time I went to the pharmacy. They had no idea what I was talking about and had to call radiology. Both departments acted as if they never had children drink this for scans. Finally I got it from the pharmacy. The next time I went to the pharmacy, they told me they NOW have it in the Radiology dept. When I went there they said to go to the pharmacy. At that point I told them they would need to locate it. Eventually they found "one" informed employee who got it for us IN the radiology dept. Now each time I go, they seem to have their act together. I guess we got caught in the middle while they changed procedures. Although they do not treat exclusively children, it is a childrens hospital attached with an adult facility. I can't understand with the volume of children that they have, they could be so confused."
- "We had this problem but it was multiplied by the fact that our insurance company switched hospitals (the new one had the lowest bid obviously) and we had to start all over, trying to get the radiology department to allow her to drink the better tasting stuff."
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)