单选题 Since the first brain scanner was constructed several years ago, computed tomography or computed medical imagery, has become fairly widely used. Its rapid acceptance is due to the fact that it has overcome several of the drawbacks of conventional X-ray technology.
To begin with, conventional two-dimensional X-ray pictures cannot show all of the information contained in a three-dimensional object. Things at different depths are super imposed, causing confusion to the viewer. Computed tomography can give three-dimensional information. The computer is able to reconstruct pictures of the body"s interior by measuring the varying intensities of X-ray beams passing through sections of the body from hundreds of different angles. Such pictures are based on series of thin "slices".
In addition, conventional X-ray generally differentiates only between bone and air, as in the chest and lungs. They cannot distinguish soft tissues or variations in tissues. The liver and pancreas are not discernible at all, and certain other organs max only be rendered visible through the use of radio paque dye. Since computed tomography is much more sensitive, the soft tissues of the kidneys or the liver can be seen and clearly differentiated. This technique can also accurately measure different degrees of X-ray absorption, facilitating the study of the nature of tissue.
A third problem with conventional X-my methods is their inability to measure quantitatively the separate densities of the individual substances through which the X-ray has passed. Only the mean absorption of all the tissues is recorded. This is not a problem with computed tomography. It can accurately locate a tumor and subsequently monitor the progress of radiation treatment, so that in addition to its diagnostic capabilities, it can play a significant role in therapy.
单选题 Conventional X-rays mainly show the difference between ______.
【正确答案】 A
【答案解析】[解析] 细节题。答案源自于文章第三段第一句话“conventional X-ray generally differentiates only between bone and air”即传统的X光线通常只能显示出骨骼与气体之间的不同。故答案为A。
单选题 What kind of view is made possible by contiguous cross sections of the body?
【正确答案】 B
【答案解析】[解析] 细节题。根据文章第二段中“Things at different depths are super imposed, causing confusion to the viewer. Computed tomography can give three-dimensional information. ”可知，正是身体中相邻的横截面证实了三维立体这种视觉效果，使其成为可能。故答案为B。
单选题 It can be inferred from the passage that compared to conventional X-ray techniques, computed tomography is more ______.
【正确答案】 D
【答案解析】[解析] 推理题。从文章第三段的前两句话可以得出，传统的X光技术只能拍摄出二维的照片，而新型的电脑断层摄影能拍摄出三维的图片，因而可以提供更多的信息，故答案为D。
单选题 What is the author"s attitude toward this new technique?
【正确答案】 C
【答案解析】[解析] 态度题。文中作者一直在描述新技术相比于旧技术而言的优越性。可见作者对这种新技术的态度既非小心谨慎的，也非容忍的、批判的，而是充满热情的，故答案为C。
单选题 According to the passage, computed tomography can be used for all of the following EXCEPT ______.
【正确答案】 D
【答案解析】[解析] 推理题。根据文章大意，我们可以知道电脑断层摄影是一种新型X光技术，能够帮助人们利用三维图片看清身体的构造。故电脑断层技术可以帮助医生监测病人的疾病情况、诊断身体异常、确定癌症的位置。而D项，修复被损坏的组织则不是仅仅使用电脑断层摄影就可以实现的。故答案为D。