Read the following passage.
A. The story of medical X-rays began on the evening of November 8, 1895. Wilhelm Röntgen was studying electric currents passing through gas at very low pressure. Although his tube was sealed inside thick black card, a screen coated with barium platinocyanide began to glow as far as two metres away. He found that objects of different thickness let the rays through by different amounts, and he recorded an image of his wife's hand that showed the shadows of her bones and of a ring. Because the nature of the rays was unknown, he called them X-rays.
B. An ordinary X-ray picture, called radiography, is made by passing a beam through the body. Internal structures absorb or scatter part of the beam, and the pattern that remains reaches a detector, such as film or a computer screen. In radiography a single image is recorded for later study, and mammography is a special kind of radiography used for the breasts. Fluoroscopy instead shows a continuous image on a monitor, so staff can follow a procedure or a contrast dye in real time. X-ray exams help diagnose disease without pain and guide doctors as they place devices such as stents inside the body.
C. The invention of computed tomography, or CT, was another major advance. In a CT scan, the detector circles the patient while many X-ray images are taken, and a computer turns them into cross-sectional slices of organs and tissues. Because each CT image is built from many separate projections, the exam gives a higher dose than conventional radiography. Typical organ doses are about 0.01 millisieverts for a dental X-ray, 0.1 for a chest X-ray and 10 for an adult abdominal CT. Medical procedures account for roughly 40 per cent of an average person's yearly radiation dose.
D. X-rays are ionizing radiation, which carries enough energy to damage DNA. This brings a small increase in the chance of developing cancer later in life. The lifetime risk grows with the dose and the number of exams, and it is larger for people who are X-rayed when young, so extra care is taken with children and pregnant patients. Doctors are advised to order an exam only when it is needed, to consider options that use less or no radiation, such as ultrasound or MRI, and to check a patient's imaging history to avoid repeating a test. Skin reddening and other tissue effects are rare in ordinary exams but can follow long, complex fluoroscopy procedures.
E. Not given in any of the above paragraphs.
Decide which paragraph, A to D, has the information given in each statement below. Select E if the information is not given in any of the paragraphs.
AI explanationShows the answer. Tap to open.
Correct Answer: D
Why this is correct: Paragraph D says the lifetime risk of cancer grows with dose and number of exams. It also says the risk is larger for people who are X-rayed when young. So exposure early in life means a greater risk.
Passage Reference: The lifetime risk grows with the dose and the number of exams, and it is larger for people who are X-rayed when young, so extra care is taken with children and pregnant patients.
Tips: Find where age is linked to the danger of cancer. Check whether being young makes that danger bigger or smaller.
Why the other options are wrong:
- A: Paragraph A tells how the rays were found in 1895. Nobody's age or health risk is discussed.
- B: Paragraph B explains how an image is formed on a detector, with no mention of cancer or age.
- C: Paragraph C lists doses for different exams, but it does not say that younger people face a larger risk from them.
- E: The larger risk for people X-rayed when young is stated in the middle of Paragraph D.
Correct Answer: B
Passage Reference: Fluoroscopy instead shows a continuous image on a monitor, so staff can follow a procedure or a contrast dye in real time.
Why this is correct: Paragraph B says fluoroscopy shows a continuous image on a monitor. So staff can follow a procedure or a contrast dye in real time. Watching as it happens is what real time means.
Tips: Fluoroscopy is named more than once. Ask which mention explains what staff can watch while a procedure happens.
Why the other options are wrong:
- A: Paragraph A describes a single early image of a hand, not a live picture used during a procedure.
- C: Paragraph C describes CT slices built by a computer from many images, which is not the same as watching live.
- D: Fluoroscopy comes up in Paragraph D only as a cause of rare skin effects. It does not explain what the exam shows.
- E: The continuous image that lets staff follow a procedure in real time is described in Paragraph B.
Correct Answer: D
Passage Reference: Doctors are advised to order an exam only when it is needed, to consider options that use less or no radiation, such as ultrasound or MRI, and to check a patient's imaging history to avoid repeating a test.
Why this is correct: Paragraph D says doctors are advised to check a patient's imaging history to avoid repeating a test. Knowing what was already done keeps the same exam from being ordered again.
Tips: The statement is about not ordering the same exam twice. Find where a patient's earlier pictures come up, and check what they are used for.
Why the other options are wrong:
- A: The first experiments in 1895 fill paragraph A. No patient records are mentioned there.
- B: In Paragraph B a single image is recorded for later study. But that is about one exam, not a list of past exams.
- C: Notice that paragraph C compares the doses of different exams, but it says nothing about avoiding repeats.
- E: Checking a patient's imaging history to avoid repeating a test is advice given in Paragraph D.
Correct Answer: A
Passage Reference: Wilhelm Röntgen was studying electric currents passing through gas at very low pressure.
Why this is correct: Paragraph A says Wilhelm Röntgen was studying electric currents passing through gas at very low pressure. Then a screen nearby began to glow. He was working on a different question when he found the rays.
Tips: Look for what the scientist was actually studying at the time.
Why the other options are wrong:
- B: The second paragraph explains how the rays are used to make pictures now. It does not say how they were first found.
- C: Look at paragraph C: it calls CT a major advance and explains how it works. But it does not say how X-rays were first found.
- D: Look at paragraph D: it covers modern risks and advice to doctors, not the history of the discovery.
- E: In paragraph A, the writer says Röntgen was studying electric currents in gas when he came across the rays.
Correct Answer: C
Passage Reference: Because each CT image is built from many separate projections, the exam gives a higher dose than conventional radiography.
Why this is correct: The third paragraph explains that each CT image is built from many separate projections. Because of this, the exam gives a higher dose than conventional radiography. Conventional radiography is the ordinary X-ray picture.
Tips: Notice that paragraph B defines the ordinary X-ray. The comparison with CT comes later.
Why the other options are wrong:
- A: Paragraph A covers the discovery and the first image of a hand. CT and doses do not appear.
- B: Look at paragraph B: it explains ordinary radiography, but it never compares its dose with CT.
- D: Notice that paragraph D says risk rises with dose, yet it does not say which exam gives the larger dose.
- E: The comparison between the dose from CT and from conventional radiography is made in Paragraph C.
Correct Answer: E
Passage Reference: The story of medical X-rays began on the evening of November 8, 1895.
Why this is correct: Paragraph A gives the date, November 8, 1895, and describes the tube, the glowing screen and the image of a hand. It never says where Röntgen was working, so no laboratory or country is given.
Tips: The first paragraph gives you when. Check whether it also gives you where.
Why the other options are wrong:
- A: The first paragraph is the nearest because it tells the story of the discovery. But it gives a date and no place at all.
- B: In paragraph B, the writer explains how images are made today and names no laboratory.
- C: The third paragraph is about CT and doses. It does not mention where anything was discovered.
- D: The fourth paragraph gives risks and advice for doctors, with no country or laboratory named.
Correct Answer: C
Passage Reference: Medical procedures account for roughly 40 per cent of an average person's yearly radiation dose.
Why this is correct: Look at paragraph C: it says medical procedures account for roughly 40 per cent of an average person's yearly radiation dose. Two fifths of the total is a large part.
Tips: The fourth paragraph talks about dose too. Look for a share of the whole year.
Why the other options are wrong:
- A: The first paragraph stays in 1895 with the first image. It gives no yearly dose for anyone.
- B: The second paragraph describes how an image forms and what exams are for, not how much radiation people receive.
- D: The fourth paragraph says risk grows with dose and number of exams, but it gives no share of a person's total radiation.
- E: The figure of roughly 40 per cent of a person's yearly dose closes Paragraph C.
Correct Answer: A
Passage Reference: He found that objects of different thickness let the rays through by different amounts, and he recorded an image of his wife's hand that showed the shadows of her bones and of a ring.
Why this is correct: In paragraph A, Röntgen recorded an image of his wife's hand. It showed the shadows of her bones and of a ring. A ring is a piece of jewellery.
Tips: Find the story of the very first pictures. Ask what the person's hand showed, and what else could be seen on it.
Why the other options are wrong:
- B: Notice that paragraph B explains how internal structures absorb the beam, but it describes no particular image.
- C: The third paragraph describes slices of organs made by CT, not a picture of a hand.
- D: Risk is the subject of paragraph D. The paragraph mentions skin reddening, but it describes no early picture of a hand or a ring.
- E: The image of Röntgen's wife's hand, with her bones and a ring, is described in Paragraph A.
Correct Answer: E
Passage Reference: Doctors are advised to order an exam only when it is needed, to consider options that use less or no radiation, such as ultrasound or MRI, and to check a patient's imaging history to avoid repeating a test.
Why this is correct: In paragraph D, the writer says doctors should consider options that use less or no radiation, such as ultrasound or MRI. It also says extra care is taken with children. It gives radiation as the reason, and cost is never mentioned.
Tips: The fourth paragraph does name ultrasound. Ask what reason it gives for choosing it.
Why the other options are wrong:
- A: Paragraph A is set in 1895 and mentions no other kind of exam.
- B: Look at paragraph B: it compares radiography, mammography and fluoroscopy. Ultrasound and prices do not appear.
- C: In paragraph C, the writer talks about doses in millisieverts, not about what an exam costs.
- D: Ultrasound and children both appear in Paragraph D, but its reason for other exams is less radiation, not lower cost.
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