Radiotherapy: linear accelerator: practice question

A Radiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Radiology · Radiotherapy: linear accelerator

Sample item

Which of the following is an advantage of a linear accelerator compared with a cobalt unit?

AAbsence of electrical power needsBA constant dose rate that decays with timeCLower cost with simple maintenanceDHigher energy beams with sharper penumbra and no radioactive source to replace

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Higher energy beams with sharper penumbra and no radioactive source to replace

Linacs generate megavoltage X-rays and electron beams of variable energy, with a small focal spot and sharp field edges. They do not need periodic source replacement. A cobalt unit decays about 1 percent a month and is simpler and cheaper.

Option by option

A. Absence of electrical power needs
Linacs require considerable electrical power.
B. A constant dose rate that decays with time
A decaying dose rate is a feature of cobalt, not linac.
C. Lower cost with simple maintenance
Cobalt units are the cheaper ones.
D. Higher energy beams with sharper penumbra and no radioactive source to replace (correct)
Correct. Linacs offer variable high energies, sharp fields and no source decay.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is D, Higher energy beams with sharper penumbra and no radioactive source to replace. Linacs generate megavoltage X-rays and electron beams of variable energy, with a small focal spot and sharp field edges.

Why is "Absence of electrical power needs" not the answer?

Linacs require considerable electrical power.

Why is "A constant dose rate that decays with time" not the answer?

A decaying dose rate is a feature of cobalt, not linac.

Why is "Lower cost with simple maintenance" not the answer?

Cobalt units are the cheaper ones.

What concept does this question test?

It tests Radiotherapy: linear accelerator in Radiology. They do not need periodic source replacement. A cobalt unit decays about 1 percent a month and is simpler and cheaper.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Radiotherapy: linear accelerator?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.