Imaging modalities and physics: mechanical index: 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 · Imaging modalities and physics: mechanical index

Sample item

A sonographer is scanning a fetus and wants to reduce the risk of acoustic cavitation. Which on-screen output index relates to this bioeffect?

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

The answer and the reasoning

C. Mechanical index

The mechanical index reflects the peak negative pressure of the pulse and the risk of non-thermal cavitation. The thermal index estimates tissue heating, and both are kept as low as reasonably achievable in obstetric scanning.

Option by option

  • A. Thermal index

    The thermal index estimates the potential temperature rise of tissue and does not predict cavitation.

  • B. Pulse repetition frequency

    Pulse repetition frequency sets how often pulses are sent and is not a safety index.

  • C. Mechanical index (correct)

    Correct. The mechanical index predicts cavitation risk.

  • D. Time-gain compensation

    Time-gain compensation adjusts echo amplification with depth and has no safety meaning.

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, Mechanical index. The mechanical index reflects the peak negative pressure of the pulse and the risk of non-thermal cavitation.

Why is "Thermal index" not the answer?

The thermal index estimates the potential temperature rise of tissue and does not predict cavitation.

Why is "Pulse repetition frequency" not the answer?

Pulse repetition frequency sets how often pulses are sent and is not a safety index.

Why is "Time-gain compensation" not the answer?

Time-gain compensation adjusts echo amplification with depth and has no safety meaning.

What concept does this question test?

It tests Imaging modalities and physics: mechanical index in Radiology. The thermal index estimates tissue heating, and both are kept as low as reasonably achievable in obstetric scanning.

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 Imaging modalities and physics: mechanical index?

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.