Sajjad1994
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. 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. 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 alter 1894
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. 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. 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. 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. 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. 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
1. Which of the following best summarizes the author's main point?The passage starts by introducing the concept of imaging technology and then talks about two technologies - X-Ray and CT. The second line of the first paragraph provides us a clue - "
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." - that the passage is likely going to explain us about computed tomography.
(A) The introduction of x—ray techniques into medicine virtually revolutionized the field.
While the passage does mention about CT Scans this is not the the primary purpose. The introduction to X-Ray was only to create a base for the passage.
(B) Without replacing x—ray techniques, the development of CT has widened the scope of imaging technologyThis is indeed a correct option. The passage opens with the concept of X-Rays but then goes about explaining how Computed tomography (CT) offers an advancement in producing a visual image of body organs.
(C) Although CT has many virtues, it has some major drawbacks as well
The passage doesn't contrast anything on the CT scans. Hence, this is an incorrect option.
(D) Imaging techniques have permitted physicians to diagnose many internal disorders without surgery.
While this is true and the passage opens with this idea, the main purpose of the passage is not to convey this message.
(E) The most important factor in assessing the value of imaging techniques is speed.
This is not correct. The reference to speed is done only to explain CT scans and X-Rays.
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
Correct. Refer to the part of the passage "
which first allowed physicians to peer into"
(B) is the most popular of the imaging techniques
Correct. Refer to the part of the passage "
remain the most widely used imaging technique"
(C) records virtually all transmitted radiationThis is incorrect. The passage mentions "
can register more than 60 percent of the radiation striking them". Hence x-ray cannot record all transmitted radiations.
(D) produces images rapidly
Correct. Refer to the part of the passage "
The great advantage of film techniques is the relatively short time it takes to acquire a complete image"
(E) was developed alter 1894
Correct. Refer to the part of the passage "
The field of imaging technology began in 1895"
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 bodyThis is a correct option. The passage mentions "
can register more than 60 percent of the radiation striking them". This means some of the x-ray is lost (scattered). Hence, this information is inline with the detail mentioned in the passage.
(B) is accurately maintained at an extremely narrow width
This information is in reference to CT scans. Eliminate B.
(C) requires a great deal of energy to operate
No information is mentioned with respect to the energy used in x-ray imaging. Hence, we can eliminate this option.
(D) can be moved rapidly from one part of the body to another
The passage mentions that the images can be repeated. Refer "
images can be repeated—uup to 60 times per second". The passage doesn't mention that the x-ray imaging can be moved from one part of the body to another. This is incorrect.
(E) is mostly absorbed by the tissue of the body
No information on the abosorption is mentioned in the passage. Hence, this option is incorrect.
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
This is incorrect. The screen captures the rays, not monitors.
(B) hold in place the light-sensitive film for the X—ray image
This is not correct. The information provided in the passage doesn't state anything on the amount of light held. Hence, we can eliminate this option.
(C) allow the physician to judge immediately the quality of the X—ray image
No such information is provided in the passage. Hence, we can eliminate C.
(D) produce an image of the irradiated organ for the filmThis is inline with the details mentioned in the passage "
hereby producing a two—dimensional image of a three—dimensional structure". Hence, the fluorescent screen in conventional x—ray imaging is responsible for creating an image of the organ.
(E) control the speed at which an image is produced
This is not correct. The speed at which image is produced is not controlled by the fluorescent screen.
5. According to the passage, CT imaging has been particularly useful forThe answer to this question is mentioned in the last line of the passage "
and for evaluating certain kinds of cancers"
(A) imaging the lungs
Incorrect. Eliminate A.
(B) analyzing some cancersTrue, as mentioned above the details is mentioned in the passage.
(C) diagnosing bone injuries
Incorrect. The passage doesn't mention this information.
(D) observing the muscles of the heart during contraction
The reference to heart in the passage is for x-rays. Eliminate D.
(E) studying the motions of the stomach during digestion
No such information is provided in the passage. Hence, eliminate E.
6. The passage would most likely appear in a(A) science magazine for nonspecialistsThis seems correct. The information is simple enough and doesn't delve into technicalities of x-ray or CT scan.
(B) textbook on radiation physics
The details presented on the passage is not limited to radiation. The information presented is generic. Eliminate B.
(C) medical research journal
The details mentioned in the passage is not of research nature, i.e. the passage doesn't mention of an experiment or conclusion that anyone has made. Hence, we can eliminate this.
(D) CT users' manual
This is incorrect. The details presented the passage is non technical. Hence, such information cannot be a part of the user manual.
(E) monograph on early twentieth—century medical technology
This doesn't seem to be the case. We can eliminate this option.
7. It can be inferred from the passage that CT is extremely valuable for imaging the brain primarily becauseThe answer to this question lies in "
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"
(A) tomograms of the brain give the best picture of the activities of the brain
The passages doesn't mention that tomograms gives the best picture. The passage merely compares the images produced by CT scans with X-rays. Hence, we can eliminate A.
(B) the brain is composed of tissues whose contrast differences are not very greatThis is correct. The highligted part mentions that information.
(C) only relatively slow imaging techniques can produce medically useful images of the brain
This is not correct. We can eliminate C.
(D) better images can be constructed out of profiles of the relatively small brain than out of profiles of larger areas of the body
No such information can be inferred from the passage. We can eliminate D.
(E) x—rays are unable to penetrate the skull sufficiently to obtrain a sharp picture of the brain
No such details is presented in the passage. We can eliminate E.
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
This is incorrect. CT scans registers the images in layers. Hence, we can eliminate A.
(B) Studying an orange by peeling it
This option is a tricky one. While the option talks about layers, CT scans registers the body as thin indivdual slices. The option is close, but D seems better.
(C) Characterizing a crystal by measuring the angle between two faces
This is not correct. We can eliminate C.
(D) Studying a tree trunk by making slices through the trunkThis is correct. Refer to the last paragraph "
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"
(E) Learning about a coconut by drilling a hole in it
Incorrect. CT scans views the body as series of layers. Hence, we can eliminate this option.
Answers
1. B
2. C
3. A
4. D
5. B
6. A
7. B
8. D