Imaging modalities and physics: kVp and radiographic contrast: 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: kVp and radiographic contrast

Sample item

A chest radiograph is deliberately taken at about 120 kVp rather than 70 kVp. What is the expected change in the image?

AHigher subject contrast, with better rib detailBGreater scatter removal by the lungsCLower subject contrast, with better visibility through the mediastinum and less rib conspicuityDHigher patient dose for the same image receptor exposure

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

The answer and the reasoning

C. Lower subject contrast, with better visibility through the mediastinum and less rib conspicuity

A higher kVp lowers the photoelectric fraction, so differences between bone and soft tissue shrink. The wider range of grey levels shows lung and mediastinal structures through the heart while ribs are less obtrusive.

Option by option

A. Higher subject contrast, with better rib detail
Rib contrast falls at high kVp since photoelectric absorption in bone falls.
B. Greater scatter removal by the lungs
Scatter rises at high kVp, and it is not removed by the lungs.
C. Lower subject contrast, with better visibility through the mediastinum and less rib conspicuity (correct)
Correct. High kVp flattens bone-soft tissue contrast and gives better penetration.
D. Higher patient dose for the same image receptor exposure
A more penetrating beam usually needs less mAs, and dose to the receptor can be kept the same with lower patient dose.

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 C, Lower subject contrast, with better visibility through the mediastinum and less rib conspicuity. A higher kVp lowers the photoelectric fraction, so differences between bone and soft tissue shrink.

Why is "Higher subject contrast, with better rib detail" not the answer?

Rib contrast falls at high kVp since photoelectric absorption in bone falls.

Why is "Greater scatter removal by the lungs" not the answer?

Scatter rises at high kVp, and it is not removed by the lungs.

Why is "Higher patient dose for the same image receptor exposure" not the answer?

A more penetrating beam usually needs less mAs, and dose to the receptor can be kept the same with lower patient dose.

What concept does this question test?

It tests Imaging modalities and physics: kVp and radiographic contrast in Radiology. The wider range of grey levels shows lung and mediastinal structures through the heart while ribs are less obtrusive.

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: kVp and radiographic contrast?

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.