Imaging physics: radiolucent versus radiopaque: 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 physics: radiolucent versus radiopaque

Sample item

Arrange these in order of increasing radiographic density (blackest to whitest) on a plain film.

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

The answer and the reasoning

C. Air, fat, water (soft tissue), bone, metal

The five basic radiographic densities are air (black), fat (dark grey), soft tissue or fluid (grey), bone (white) and metal (brightest). This order is used to interpret radiographs. Fat's lower density against soft tissue is the reason fat planes can be seen.

Option by option

  • A. Water, air, fat, metal, bone

    Water is denser than air and fat, and bone lies below metal.

  • B. Fat, air, bone, water, metal

    Fat is denser than air, not less.

  • C. Air, fat, water (soft tissue), bone, metal (correct)

    Correct. This is the standard order from least to most dense.

  • D. Metal, bone, water, fat, air

    This is the reverse of the correct sequence.

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 C, Air, fat, water (soft tissue), bone, metal. The five basic radiographic densities are air (black), fat (dark grey), soft tissue or fluid (grey), bone (white) and metal (brightest).

Why is "Water, air, fat, metal, bone" not the answer?

Water is denser than air and fat, and bone lies below metal.

Why is "Fat, air, bone, water, metal" not the answer?

Fat is denser than air, not less.

Why is "Metal, bone, water, fat, air" not the answer?

This is the reverse of the correct sequence.

What concept does this question test?

It tests Imaging physics: radiolucent versus radiopaque in Radiology. This order is used to interpret radiographs. Fat's lower density against soft tissue is the reason fat planes can be seen.

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 physics: radiolucent versus radiopaque?

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.