Imaging modalities and physics: signal void of cortical bone: 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: signal void of cortical bone

Sample item

On MRI, a dense cortical bone margin and a calcified nodule both appear black on T1, T2 and FLAIR images. What is the physical reason?

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

The answer and the reasoning

B. They contain very few mobile protons and have extremely short T2 relaxation, so little signal is detected

MRI signal comes from mobile hydrogen protons. Dense cortex and calcification have few such protons and a very short T2, so the signal decays before it can be read. This is why CT is preferred to show calcification and cortical detail.

Option by option

  • A. They have a very long T1 that is never recovered

    A very long T1 relates to fluids, not to dense bone.

  • B. They contain very few mobile protons and have extremely short T2 relaxation, so little signal is detected (correct)

    Correct. Few mobile protons and very short T2 give a signal void.

  • C. They contain paramagnetic ions that enhance T1

    Paramagnetic ions would increase signal rather than abolish it.

  • D. They absorb the radiofrequency pulse completely and heat up

    RF energy is not simply absorbed to give black signal; the issue is lack of detectable signal.

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, They contain very few mobile protons and have extremely short T2 relaxation, so little signal is detected. MRI signal comes from mobile hydrogen protons.

Why is "They have a very long T1 that is never recovered" not the answer?

A very long T1 relates to fluids, not to dense bone.

Why is "They contain paramagnetic ions that enhance T1" not the answer?

Paramagnetic ions would increase signal rather than abolish it.

Why is "They absorb the radiofrequency pulse completely and heat up" not the answer?

RF energy is not simply absorbed to give black signal; the issue is lack of detectable signal.

What concept does this question test?

It tests Imaging modalities and physics: signal void of cortical bone in Radiology. Dense cortex and calcification have few such protons and a very short T2, so the signal decays before it can be read. This is why CT is preferred to show calcification and cortical detail.

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: signal void of cortical bone?

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.