MRI: chemical shift 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.

Try it

Radiology · MRI: chemical shift artefact

Sample item

On an abdominal MRI, a bright band and a dark band appear at opposite borders of the kidney where it abuts retroperitoneal fat, along the frequency-encoding direction. What is this artefact?

AChemical shift artefact from different resonant frequencies of fat and water protonsBSusceptibility artefact from a metal clipCTruncation ringing from low matrix sizeDAliasing from a field of view smaller than the patient

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

The answer and the reasoning

A. Chemical shift artefact from different resonant frequencies of fat and water protons

Fat and water protons precess at slightly different frequencies, so at their interface the signals are misregistered along the frequency-encoding axis. This yields paired bright and dark edges, and the effect grows at higher field strength.

Option by option

A. Chemical shift artefact from different resonant frequencies of fat and water protons (correct)
Correct. Fat-water frequency difference displaces signal at the interface.
B. Susceptibility artefact from a metal clip
Metal clips cause signal voids with distortion, not paired edge bands.
C. Truncation ringing from low matrix size
Truncation causes parallel lines near sharp edges, not paired bright and dark bands.
D. Aliasing from a field of view smaller than the patient
Aliasing wraps anatomy from outside the field of view into the image, usually along the phase direction.

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 A, Chemical shift artefact from different resonant frequencies of fat and water protons. Fat and water protons precess at slightly different frequencies, so at their interface the signals are misregistered along the frequency-encoding axis.

Why is "Susceptibility artefact from a metal clip" not the answer?

Metal clips cause signal voids with distortion, not paired edge bands.

Why is "Truncation ringing from low matrix size" not the answer?

Truncation causes parallel lines near sharp edges, not paired bright and dark bands.

Why is "Aliasing from a field of view smaller than the patient" not the answer?

Aliasing wraps anatomy from outside the field of view into the image, usually along the phase direction.

What concept does this question test?

It tests MRI: chemical shift artefact in Radiology. This yields paired bright and dark edges, and the effect grows at higher field strength.

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 MRI: chemical shift 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.