Computed tomography: 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 · Computed tomography

Sample item

What Hounsfield unit value is assigned approximately to pure water on CT?

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

The answer and the reasoning

C. 0

The Hounsfield scale is calibrated so water is approximately 0 HU, air is near -1000 HU, and dense cortical bone is strongly positive, helping distinguish tissues on computed tomography.

Option by option

  • A. +50,000

    This value is far outside the conventional Hounsfield scale.

  • B. -1000

    Air is near -1000 HU on the CT scale.

  • C. 0 (correct)

    Correct: water is the 0 HU reference point.

  • D. +1000

    Dense bone is closer to +1000 HU than water.

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.

More Radiology questions

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is C, 0. The Hounsfield scale is calibrated so water is approximately 0 HU, air is near -1000 HU, and dense cortical bone is strongly positive, helping distinguish tissues on computed tomography.

Why is "+50,000" not the answer?

This value is far outside the conventional Hounsfield scale.

Why is "-1000" not the answer?

Air is near -1000 HU on the CT scale.

Why is "+1000" not the answer?

Dense bone is closer to +1000 HU than water.

What concept does this question test?

It tests Computed tomography in Radiology. The correct option holds because: Correct: water is the 0 HU reference point.

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 Computed tomography?

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.