Imaging modalities and physics: MRI zipper 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: MRI zipper artefact

Sample item

A brain MRI shows a narrow line of alternating bright and dark pixels running across the whole image at a fixed position. The scanner room door was found slightly open. Which artefact is this?

AAliasing (wrap-around) of anatomy outside the field of viewBZipper artefact from radiofrequency leakage into the roomCGibbs ringing at a sharp tissue interfaceDChemical shift artefact at a fat-water boundary

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

The answer and the reasoning

B. Zipper artefact from radiofrequency leakage into the room

External radiofrequency noise entering through a faulty door seal or unshielded cable adds a signal at a single frequency, producing a zipper-like line across the image. It is fixed by closing the room and repairing the shielding. The other artefacts arise from the imaging process itself and are tied to anatomy.

Option by option

A. Aliasing (wrap-around) of anatomy outside the field of view
Aliasing folds anatomy from outside the field of view onto the image.
B. Zipper artefact from radiofrequency leakage into the room (correct)
Correct. Stray radiofrequency at one frequency appears as a zipper line.
C. Gibbs ringing at a sharp tissue interface
Gibbs ringing gives parallel lines next to a sharp edge, following anatomy.
D. Chemical shift artefact at a fat-water boundary
Chemical shift artefact gives a bright and dark band at fat-water interfaces.

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.

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is B, Zipper artefact from radiofrequency leakage into the room. External radiofrequency noise entering through a faulty door seal or unshielded cable adds a signal at a single frequency, producing a zipper-like line across the image.

Why is "Aliasing (wrap-around) of anatomy outside the field of view" not the answer?

Aliasing folds anatomy from outside the field of view onto the image.

Why is "Gibbs ringing at a sharp tissue interface" not the answer?

Gibbs ringing gives parallel lines next to a sharp edge, following anatomy.

Why is "Chemical shift artefact at a fat-water boundary" not the answer?

Chemical shift artefact gives a bright and dark band at fat-water interfaces.

What concept does this question test?

It tests Imaging modalities and physics: MRI zipper artefact in Radiology. It is fixed by closing the room and repairing the shielding. The other artefacts arise from the imaging process itself and are tied to anatomy.

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: MRI zipper 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.