Radiation safety and radiobiology: biological dosimetry: 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 safety and radiobiology: biological dosimetry

Sample item

A worker may have received a significant whole-body exposure from a lost source, but wore no dosimeter. Which blood test helps estimate the absorbed dose?

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

The answer and the reasoning

C. Dicentric chromosome count in cultured lymphocytes

Ionising radiation produces dicentric chromosomes in circulating lymphocytes, and their frequency rises with dose, so the dicentric assay is the standard biological dosimeter. Serial lymphocyte counts are also useful, but a single early leucocyte count is not reliable. Ferritin and urinary iodine have no dose relationship.

Option by option

  • A. Total leucocyte count at one hour

    A single early leucocyte count is non-specific and changes with stress.

  • B. Urinary iodine excretion

    Urinary iodine reflects iodine intake or radioiodine handling, not whole-body dose.

  • C. Dicentric chromosome count in cultured lymphocytes (correct)

    Correct. The dicentric frequency in lymphocytes correlates with absorbed dose.

  • D. Serum ferritin

    Ferritin reflects iron stores and is not dose dependent.

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, Dicentric chromosome count in cultured lymphocytes. Ionising radiation produces dicentric chromosomes in circulating lymphocytes, and their frequency rises with dose, so the dicentric assay is the standard biological dosimeter.

Why is "Total leucocyte count at one hour" not the answer?

A single early leucocyte count is non-specific and changes with stress.

Why is "Urinary iodine excretion" not the answer?

Urinary iodine reflects iodine intake or radioiodine handling, not whole-body dose.

Why is "Serum ferritin" not the answer?

Ferritin reflects iron stores and is not dose dependent.

What concept does this question test?

It tests Radiation safety and radiobiology: biological dosimetry in Radiology. Serial lymphocyte counts are also useful, but a single early leucocyte count is not reliable. Ferritin and urinary iodine have no dose relationship.

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 Radiation safety and radiobiology: biological dosimetry?

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.