The field of imaging technology began in 1895 with the discovery of x—rays, which first allowed physicians to peer into their patients without surgery. In recent decades there have been enormous advances in imaging technology; not only have x—ray techniques been vastly improved, but new methods, especially computed tomography, have been introduced. Although there has been some debate, most doctors agree that each imaging technique possesses some property that makes it uniquely useful, and no single method has prevailed to the exclusion of others. X—rays remain the most widely used imaging technique. The technique consists of irradiating the relevant part of the body with an x—ray source and allowing the x—rays that are transmitted to strike an x-ray-sensitive fluorescent screen, which then balkens a sheet of light—sensitive film, thereby producing a two—dimensional image of a three—dimensional structure. Today fluorescent screen film combinations can register more than 60 percent of the radiation striking them. Consequently, even fairly small differences in the distribution of the transmitted x—rays can be discerned. Although film techniques are very effective for imaging parts of the body with high contrast, such as lungs and bones, they are limited in their capacity for imaging organs of low contrast, such as kidneys and gallbladders. The great advantage of film techniques is the relatively short time it takes to acquire a complete image, and the consequent high rate at which images can be repeated—uup to 60 times per second, an advantage for viewing the heart and other rapidly moving organs. Computed tomography (CT) offers a most exciting refinement in producing a visual image of body organs. Instead of compressing a three—dimensional structure into a two-dimensional image, CT uses an extremely narrow beam to produce a sequence of profiles that can be combined into an image, or tomogram, of a thin slice of the body. These images are more readily comprehended than conventional x—ray images because confusion caused by superimposition is eliminated, and because the narrowness of the beam markedly decreases the registration of scattered rays, thus improving the image contrast. CT imaging is more time—consuming than imaging on film, because irradiation and data acquisition usually take a relatively slow 2 to 10 seconds per slice and, without special computers, the mathematical process for reconstructing the image requires another 15 to 30 seconds. CT also requires that the body be viewed as a series of many individual slices, but it has the unique attribute of being sensitive to extremely slight contrast differences in tissue — it can, for example, discriminate between white and gray matter in the brain. For this reason, CT has proved invaluable for imaging the brain, for diagnosing hemorrhage and stroke, and for evaluating certain kinds of cancers. 1 1. Which of the following best summarizes the author's main point? (A) The introduction of x—ray techniques into medicine virtually revolutionized the field. (B) Without replacing x—ray techniques, the development of CT has widened the scope of imaging technology (C) Although CT has many virtues, it has some major drawbacks as well (D) Imaging techniques have permitted physicians to diagnose many internal disorders without surgery. (E) The most important factor in assessing the value of imaging techniques is speed. 2 2. According to the passage, all of the following are true about conventional x—ray imaging EXCEPT that it (A) was the first imaging technique invented (B) is the most popular of the imaging techniques (C) records virtually all transmitted radiation (D) produces images rapidly (E) was developed after 1894 3 3. It can be inferred from the passage that in conventional x—ray imaging one characteristic of the beam is that it (A) undergoes significant scattering on transmission through the body (B) is accurately maintained at an extremely narrow width (C) requires a great deal of energy to operate (D) can be moved rapidly from one part of the body to another (E) is mostly absorbed by the tissue of the body 4 4. It can be inferred from the passag that one purpose of the fluorescent screen in conventional x—ray imaging is to (A) monitor the amount of radiation the patient has received (B) hold in place the light-sensitive film for the X—ray image (C) allow the physician to judge immediately the quality of the X—ray image (D) produce an image of the irradiated organ for the film (E) control the speed at which an image is produced 5 5. According to the passage, CT imaging has been particularly useful for (A) imaging the lungs (B) analyzing some cancers (C) diagnosing bone injuries (D) observing the muscles of the heart during contraction (E) studying the motions of the stomach during digestion 6 6. The passage would most likely appear in a (A) science magazine for nonspecialists (B) textbook on radiation physics (C) medical research journal (D) CT users' manual (E) monograph on early twentieth—century medical technology 7 7. It can be inferred from the passage that CT is extremely valuable for imaging the brain primarily because (A) tomograms of the brain give the best picture of the activities of the brain (B) the brain is composed of tissues whose contrast differences are not very great (C) only relatively slow imaging techniques can produce medically useful images of the brain (D) better images can be constructed out of profiles of the relatively small brain than out of profiles of larger areas of the body (E) x—rays are unable to penetrate the skull sufficiently to obtrain a sharp picture of the brain 8 8. Which of the following ways of obtaining information is most like CT imaging? (A) Learning about a house by looking in the front door (B) Studying an orange by peeling it (C) Characterizing a crystal by measuring the angle between two faces (D) Studying a tree trunk by making slices through the trunk (E) Learning about a coconut by drilling a hole in it

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The field of imaging technology began in 1895 with the discovery of

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guddo

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Hi GMATNinja, In Q8, I chose option C. I eliminated B, D, and E. These options suggest peeling, making slices, or drilling a hole, which, in my opinion, can not be compared to CT because CT is a non-invasive procedure. Between A and C - I found C stronger than A, thats why I chose A. Any insights on where I went wrong in my understanding?

8. Which of the following ways of obtaining information is most like CT imaging?

(A) Learning about a house by looking in the front door
(B) Studying an orange by peeling it
(C) Characterizing a crystal by measuring the angle between two faces
(D) Studying a tree trunk by making slices through the trunk
(E) Learning about a coconut by drilling a hole in it

You went wrong by focusing on physical invasiveness instead of the pattern of information being gathered.

CT is being compared at the level of how it learns about a 3D object: it builds understanding through thin cross-sectional slices. That is why D is best. Even though actual CT is non-invasive, the analogy does not have to match that feature.

Why C is wrong:
measuring the angle between two faces gives only an external geometric fact. It does not reveal internal structure slice by slice.

So the key correction is:
for analogy questions, match the main operating idea, not every literal detail. Here the main idea is cross-sectional imaging, which is exactly D.

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(A) science magazine for nonspecialists
Correct

Why it works:

* Matches explanatory tone
* Uses non-technical language
* Provides overview + comparison, not deep research
* Typical of popular science writing

(B) textbook on radiation physics
Wrong

Why wrong:

* Would include technical concepts (radiation theory, equations)
* Passage avoids physics depth completely
* No formulas, no scientific derivations
* Focus is application (medical imaging), not physics theory

Trap: subject match but depth mismatch

(C) medical research journal
Wrong

Why wrong:

* Research journals include data, experiments, methodology
* Passage has none of these
* Tone is explanatory, not investigative

Trap: formal tone illusion

(D) CT users' manual
Wrong

Why wrong:

* Manual would give instructions and explain how to operate CT
* Passage does NOT instruct anything
* Covers multiple techniques, not just CT

Trap: purpose mismatch (instruction vs explanation)

(E) monograph on early twentieth-century medical technology
Wrong

Why wrong:

* Passage is NOT historical analysis
* Mentions 1895 briefly → just background
* Focus is modern comparison (X-ray vs CT)
* CT is recent → not early 20th century focus

Trap: time-period distortion

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