Imaging modalities and physics: frame rate trade-off: 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: frame rate trade-off

Sample item

A paediatric cardiologist wants higher temporal resolution when imaging a rapidly beating fetal heart and narrows the sector and reduces depth. Why does the frame rate rise?

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

The answer and the reasoning

B. Fewer scan lines are needed and each pulse has a shorter round trip

Each frame needs one pulse-echo cycle per scan line, and each cycle must wait for the deepest echo to return. Fewer lines and shallower depth reduce the time per frame, so the frame rate goes up.

Option by option

  • A. The transmit frequency is raised automatically

    Frequency is selected by the operator and changing sector width does not alter it.

  • B. Fewer scan lines are needed and each pulse has a shorter round trip (correct)

    Correct. A narrow sector and less depth reduce the time needed to build each frame.

  • C. The speed of sound in the heart increases

    The speed of sound is a tissue property and does not change with sector settings.

  • D. Persistence averaging is increased

    More persistence blurs motion by averaging frames and lowers apparent temporal resolution.

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, Fewer scan lines are needed and each pulse has a shorter round trip. Each frame needs one pulse-echo cycle per scan line, and each cycle must wait for the deepest echo to return.

Why is "The transmit frequency is raised automatically" not the answer?

Frequency is selected by the operator and changing sector width does not alter it.

Why is "The speed of sound in the heart increases" not the answer?

The speed of sound is a tissue property and does not change with sector settings.

Why is "Persistence averaging is increased" not the answer?

More persistence blurs motion by averaging frames and lowers apparent temporal resolution.

What concept does this question test?

It tests Imaging modalities and physics: frame rate trade-off in Radiology. Fewer lines and shallower depth reduce the time per frame, so the frame rate goes up.

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 Imaging modalities and physics: frame rate trade-off?

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.