Radiotherapy: brachytherapy sources: 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: brachytherapy sources

Sample item

Which isotope is used in high-dose-rate remote afterloading brachytherapy and has a half-life of about 74 days?

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

The answer and the reasoning

C. Iridium-192

Iridium-192 is a compact high-activity source with a half-life of 74 days, suited to HDR afterloaders. Co-60 has a 5.3 year half-life and Cs-137 about 30 years. Radium-226 (half-life 1600 years) is obsolete because of radon leakage.

Option by option

  • A. Radium-226

    Radium-226 has a half-life of 1600 years.

  • B. Caesium-137

    Cs-137 has a half-life of about 30 years.

  • C. Iridium-192 (correct)

    Correct. Ir-192 has a half-life of about 74 days.

  • D. Cobalt-60

    Co-60 has a half-life of 5.26 years.

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.

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Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is C, Iridium-192. Iridium-192 is a compact high-activity source with a half-life of 74 days, suited to HDR afterloaders.

Why is "Radium-226" not the answer?

Radium-226 has a half-life of 1600 years.

Why is "Caesium-137" not the answer?

Cs-137 has a half-life of about 30 years.

Why is "Cobalt-60" not the answer?

Co-60 has a half-life of 5.26 years.

What concept does this question test?

It tests Radiotherapy: brachytherapy sources in Radiology. Co-60 has a 5.3 year half-life and Cs-137 about 30 years. Radium-226 (half-life 1600 years) is obsolete because of radon leakage.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: brachytherapy sources?

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.