Radiation protection: decorporation of caesium: 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 · Radiation protection: decorporation of caesium

Sample item

A worker is internally contaminated with caesium-137 from a lost sealed source. Which agent hastens faecal elimination of the radionuclide?

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

The answer and the reasoning

B. Prussian blue (ferric ferrocyanide)

Prussian blue is an insoluble compound that traps caesium in the gut and interrupts its enterohepatic recirculation, shortening its biological half-life. It is also used for thallium poisoning.

Option by option

  • A. Potassium iodide

    Potassium iodide protects only against radioiodine.

  • B. Prussian blue (ferric ferrocyanide) (correct)

    Correct. Prussian blue binds caesium in the gut and increases its faecal excretion.

  • C. DTPA given for iodine

    DTPA chelates transuranic metals such as plutonium and is not the agent for caesium.

  • D. Dimercaprol for caesium

    Dimercaprol chelates heavy metals such as arsenic and does not remove caesium.

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 B, Prussian blue (ferric ferrocyanide). Prussian blue is an insoluble compound that traps caesium in the gut and interrupts its enterohepatic recirculation, shortening its biological half-life.

Why is "Potassium iodide" not the answer?

Potassium iodide protects only against radioiodine.

Why is "DTPA given for iodine" not the answer?

DTPA chelates transuranic metals such as plutonium and is not the agent for caesium.

Why is "Dimercaprol for caesium" not the answer?

Dimercaprol chelates heavy metals such as arsenic and does not remove caesium.

What concept does this question test?

It tests Radiation protection: decorporation of caesium in Radiology. It is also used for thallium poisoning.

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 Radiation protection: decorporation of caesium?

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.