A Computer That Sees Through You
By Awake! correspondent in New Zealand
LOOKING through an oblong window, I saw a strange scene. White-gowned attendants stood around a man lying on a table. He was being fed headfirst into what looked like a giant pencil sharpener! Was this a nightmare? A scene from a science-fiction movie? What was happening?
The scene was taking place in our local hospital here in Dunedin, on the South Island of New Zealand. The huge pencil sharpener was really a type of very sophisticated X-ray machine called a CAT scanner. No, it doesn’t scan cats—at least not so far. The three letters stand for Computerized Axial Tomography. “Tomography” comes from Greek words meaning ‘to write a slice,’ and that is what a CAT scanner does. It takes X rays of a “slice” of you, salami fashion, and “writes down,” or records, what it sees.
Perhaps you think that fancy X-ray machines are of interest only to doctors and scientists, but people here are so keen about having a CAT scanner that one was bought by public subscription. The two neighboring provinces of Otago and Southland raised $2 million, N.Z., ($1,200,000, U.S.) for it, representing a contribution of more than $6 (N.Z.) from every man, woman, and child in the area. Our local university and its medical school had done much to generate such public interest in the machine, but these CATs are now multiplying all over the world. There may well be one near you.
How Does It Work?
Have you ever had an X ray taken? If so, you probably remember having to stand or lie against a large flat plate and hold very still. While you were doing that, invisible X rays passed through your body and exposed a photographic plate behind you. Where your bones got in the way, most of the X rays were stopped. Other tissues and organs, depending on their density, reduced the X rays by varying amounts. The result was a shadow picture of what was inside you, showing the bones in white and various tissues and organs in about eight shades of gray.
Conventional X rays would be fine if all your bones and organs were spread out like a window display in a shop, but, of course, they are not. Some are shyly tucked away behind others. How can their pictures be taken? They can’t be moved around like schoolboys posing for a class picture. So the photographer must move—the X rays must be taken from different angles.
In a CAT scanner, the pencil-sharpener design allows X rays to be taken from all around the body. As many as 700 different shots in over 250 shades of gray are taken of a single “slice” of you. All these pictures provide a much more detailed look at what is inside of you than was ever possible before.
Why the Computer?
Wonderful as it is to get so many X-ray pictures taken, it is quite another matter to make head or tail of all these shots. Can you picture a busy surgeon going home after a tiring day with 700 X rays of your tummy, expecting to study them overnight and be ready to perform an operation on you the next morning? ‘Not a chance,’ you might say. ‘How is he going to deal with them?’
This complicated procedure may be compared to shining a flashlight through a glass containing a cold drink with several ice cubes in it. The light would go through the glass and ice and make a pattern on a screen behind the glass. Now, suppose you rotate the flashlight and the screen around the glass while watching the changing pattern of light and shadow. Do you think you could figure out the exact shape of each ice cube?
That may seem an impossible task for you, but it is not for a computer. The information provided by the X rays is picked up by electronic sensors rather than photographic plates. By carefully comparing the X rays that come out of you with the X rays that went in, the computer can figure out what must have been inside you when the X rays passed through. Far more than simply identifying shapes, the computer is so powerful that it can even show differences between normal and clotted blood or between brain tissue and fluid. In fact, it can pick up very slight differences in tissue density that ordinary X rays would simply overlook.
How Does It Benefit You?
It is the extra detail that a CAT scan provides that makes it so popular with doctors. A CAT scan might find a small soft tissue tumor that would not have shown up in an ordinary X ray—and save a life in the process. CAT scans are also popular with patients who would much rather be “sliced” electronically than surgically. They can eliminate a great deal of risky exploratory surgery, with all its unpleasantness and complications. Those seeking to avoid such surgery, therefore, might ask their doctors if a CAT scan could do the job instead.
Even when surgery cannot be avoided, the CAT scan can help. The chairman and professor of the Department of Radiology at a university medical school pointed out that the CAT scanner can make operations more straightforward by giving the surgeons detailed information on what they will find inside you. “The scanner hands it to them on a plate,” he said, which is a big advantage to both doctor and patient.
CAT scanners have their limitations, nonetheless. Though CAT scans can find many problems, often at an early curable stage, they cannot cure anything. While they can replace a number of very uncomfortable, and sometimes dangerous, exploratory procedures, they are not always a substitute for surgery. You should not go to your doctor and demand a CAT scan every time you get a headache. Remember that all X rays carry a very slight but measurable health risk and should not be taken without good medical reasons. On the other hand, if your doctor recommends a CAT scan, be glad that this amazing technology is available to serve you.
[Picture on page 26]
Entering the CAT scanner
Camerique/H. Armstrong Roberts