Radiotherapy: planning target volume: 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: planning target volume

Sample item

In radiotherapy planning, the planning target volume is created by adding a margin to the clinical target volume. What does this margin account for?

AThe depth of the Bragg peakBTumour hypoxiaCMicroscopic disease beyond the clinical targetDSetup error and internal organ motion

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

The answer and the reasoning

D. Setup error and internal organ motion

The gross tumour volume is the visible tumour and the clinical target volume adds microscopic spread. The planning target volume then adds a margin for patient positioning uncertainty and organ movement, so the CTV receives the prescribed dose.

Option by option

A. The depth of the Bragg peak
The Bragg peak concerns protons and is not what the margin addresses.
B. Tumour hypoxia
Hypoxia is not handled by geometric margins.
C. Microscopic disease beyond the clinical target
Microscopic extension is covered by the CTV.
D. Setup error and internal organ motion (correct)
Correct. The PTV margin covers geometric uncertainty.

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, Setup error and internal organ motion. The gross tumour volume is the visible tumour and the clinical target volume adds microscopic spread.

Why is "The depth of the Bragg peak" not the answer?

The Bragg peak concerns protons and is not what the margin addresses.

Why is "Tumour hypoxia" not the answer?

Hypoxia is not handled by geometric margins.

Why is "Microscopic disease beyond the clinical target" not the answer?

Microscopic extension is covered by the CTV.

What concept does this question test?

It tests Radiotherapy: planning target volume in Radiology. The planning target volume then adds a margin for patient positioning uncertainty and organ movement, so the CTV receives the prescribed dose.

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: planning target volume?

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.