Imaging modalities and physics: magic angle artefact: 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: magic angle artefact

Sample item

On a short-TE shoulder MRI, part of a normal supraspinatus tendon near its insertion looks falsely bright, mimicking tendinopathy. The signal disappears on a long-TE sequence. Which artefact explains this?

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

The answer and the reasoning

A. Magic angle effect

Tendon collagen is highly ordered and has a very short T2, so it is normally dark. When fibres lie about 55 degrees to the main magnetic field, dipolar interactions fall and T2 lengthens, giving a bright signal on short-TE sequences. It vanishes with long TE, which separates it from true pathology.

Option by option

  • A. Magic angle effect (correct)

    Correct. Fibre orientation near 55 degrees raises signal only on short-TE images.

  • B. Gibbs truncation artefact

    Gibbs artefact gives parallel lines adjacent to sharp edges.

  • C. Chemical shift artefact

    Chemical shift artefact displaces fat and water signals at their interface.

  • D. Susceptibility artefact

    Susceptibility artefact causes signal loss and distortion near metal or air.

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, Magic angle effect. Tendon collagen is highly ordered and has a very short T2, so it is normally dark.

Why is "Gibbs truncation artefact" not the answer?

Gibbs artefact gives parallel lines adjacent to sharp edges.

Why is "Chemical shift artefact" not the answer?

Chemical shift artefact displaces fat and water signals at their interface.

Why is "Susceptibility artefact" not the answer?

Susceptibility artefact causes signal loss and distortion near metal or air.

What concept does this question test?

It tests Imaging modalities and physics: magic angle artefact in Radiology. When fibres lie about 55 degrees to the main magnetic field, dipolar interactions fall and T2 lengthens, giving a bright signal on short-TE sequences. It vanishes with long TE, which separates it from true pathology.

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: magic angle artefact?

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.