Imaging modalities and physics: grid ratio: 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: grid ratio

Sample item

Which feature makes a high grid ratio grid more efficient at cleaning up scatter than a low ratio one, at the cost of a higher dose?

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

The answer and the reasoning

A. Taller lead strips relative to the interspace distance

Grid ratio is the height of the lead strips divided by the distance between them. A higher ratio accepts a narrower cone of radiation, absorbing more scatter but also more primary radiation, and so a higher mAs is needed.

Option by option

  • A. Taller lead strips relative to the interspace distance (correct)

    Correct. Ratio is strip height divided by interspace width, and a higher ratio improves scatter removal.

  • B. Wider interspace material between strips

    A wider interspace lowers the ratio and allows more scatter through.

  • C. Use of aluminium instead of lead strips

    Aluminium interspace material is used in some grids, but the strips themselves are lead.

  • D. A lower strip frequency

    Strip frequency is the number of lines per cm and does not define the ratio.

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 A, Taller lead strips relative to the interspace distance. Grid ratio is the height of the lead strips divided by the distance between them.

Why is "Wider interspace material between strips" not the answer?

A wider interspace lowers the ratio and allows more scatter through.

Why is "Use of aluminium instead of lead strips" not the answer?

Aluminium interspace material is used in some grids, but the strips themselves are lead.

Why is "A lower strip frequency" not the answer?

Strip frequency is the number of lines per cm and does not define the ratio.

What concept does this question test?

It tests Imaging modalities and physics: grid ratio in Radiology. A higher ratio accepts a narrower cone of radiation, absorbing more scatter but also more primary radiation, and so a higher mAs is needed.

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: grid ratio?

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.