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  3. At five feet, it can warn of a tumor no bigger than a pinprick deep in the breast. It can scan the wall of a fiery industrial fu

At five feet, it can warn of a tumor no bigger than a pinprick deep in the breast. It can scan the wall of a fiery industrial fu

admin2010-05-09  3
问题     At five feet, it can warn of a tumor no bigger than a pinprick deep in the breast. It can scan the wall of a fiery industrial furnace and indicate dangerous weak spots. It can examine a human leg and show a malfunctioning blood vessel that is causing varicose veins. Incredibly, it can even take a photograph of a past event.
    This remarkable technique is called thermography, and it has given human beings a new way of seeing. Thermography depends upon the fact that all objects give off infrared energy. The strength of these infrared emissions depends on the temperature of the body from which they come.  Although scientists have long been able to measure the strength of infrared emissions, the problem was to turn these measurements into some sort of "picture".
    Attempts were not notably successful until 1965, when Dr. Ray Lawson, of Montreal, made the first thermograms of the human body. Progress in the science has been rapid ever since, as industrial companies in Europe and the United States have come up with new developments.
    Today’s thermography looks, for the most part, like a small television camera. You point it at the subject, make a few fairly simple adjustments-and on an accompanying screen appear a black-and-white heat picture of the subject. Normally the warm areas are light, the cold areas dark, and the picture looks something like an ordinary photograph negative (底片). However, in some systems, black and white are reversed, and in still others the picture comes out in brilliant colors, with the various tones representing given temperatures.
    Using one of these systems, experimenters made a picture of the past. Focusing on an empty chair after someone had been sitting in it for a few minutes; they were able to see the heat pattern left by the body, still emanating from the chair’s fabric. The picture was so clear that they could detect that the sitter’s legs had been crossed.
    Thermography’s most valuable use has been in the field of medicine. Already it has helped to save lives, and added to doctors’ skills in treating disease. It has proved especially helpful in detecting breast tumors.
    The standard examinations for breast cancer are mammography (X ray of the breast) and clinical examination. But, says Dr. Harold Izard, of Albert Einstein Medical Center in Philadelphia, who has used thermography to examine some 20,000 women for breast cancer, "The two methods do not catch everything. Thermography can indicate the possibility of some small cancers that have been missed. And it’s safe and cheap. We can do a thermogram in a couple of minutes, and although the machines cost around $30,000 each, the price of operating them is a mater of pennies. And with the addition of thermography to the other two methods, we can get about 92 percent accuracy in detecting breast cancer."
What does the thermography depend on?
选项 A、Television cameras
B、Infrared energy
C、Photograph negatives
D、Given temperatures
答案B
解析 参见文章第2段的第2行：Thermography depends upon the fact that all objects give off infrared energy(Thermography的研制依据是所有的物体释放出红外线能量这一事实。)，因此判定正确答案是B。
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