Imaging modalities and physics: STIR near metal: 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: STIR near metal

Sample item

A knee with metal hardware is imaged, and spectral fat saturation fails because of local field inhomogeneity. Which fat-suppression approach is more reliable here?

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

The answer and the reasoning

B. STIR (short tau inversion recovery)

STIR suppresses signal on the basis of the T1 of fat and not its resonant frequency, so it is little affected by field inhomogeneity. The price is lower signal-to-noise and the fact that other short-T1 tissues, such as gadolinium-enhanced ones, can also be nulled.

Option by option

  • A. Spectral presaturation of the fat peak

    Frequency-selective saturation relies on a uniform field, and it is what fails near metal.

  • B. STIR (short tau inversion recovery) (correct)

    Correct. STIR depends on T1 and not on resonance frequency, so it tolerates field errors.

  • C. Increasing the receiver bandwidth only

    A larger bandwidth reduces distortion but does not make the fat saturation work.

  • D. Opposed-phase imaging with a longer TE

    Opposed-phase imaging detects fat and water in the same voxel and does not suppress fat.

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, STIR (short tau inversion recovery). STIR suppresses signal on the basis of the T1 of fat and not its resonant frequency, so it is little affected by field inhomogeneity.

Why is "Spectral presaturation of the fat peak" not the answer?

Frequency-selective saturation relies on a uniform field, and it is what fails near metal.

Why is "Increasing the receiver bandwidth only" not the answer?

A larger bandwidth reduces distortion but does not make the fat saturation work.

Why is "Opposed-phase imaging with a longer TE" not the answer?

Opposed-phase imaging detects fat and water in the same voxel and does not suppress fat.

What concept does this question test?

It tests Imaging modalities and physics: STIR near metal in Radiology. The price is lower signal-to-noise and the fact that other short-T1 tissues, such as gadolinium-enhanced ones, can also be nulled.

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: STIR near metal?

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.