Imaging physics: anode heel effect: 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: anode heel effect

Sample item

While positioning a patient for a long-field radiograph such as a thoracic spine, the radiographer places the thicker body part towards the cathode end of the tube. This uses which principle?

AHeel effect: beam intensity is lower on the cathode sideBHeel effect: beam intensity is lower on the anode sideCInverse square lawDGrid cut-off

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

The answer and the reasoning

B. Heel effect: beam intensity is lower on the anode side

X-rays emitted toward the anode side travel through more target material at the angled anode surface and are partly absorbed, so intensity is lower there. The thicker or denser part is therefore placed under the cathode end, which has the stronger beam. The effect is more marked with small anode angles and short distances.

Option by option

A. Heel effect: beam intensity is lower on the cathode side
The cathode side has the higher, not lower, intensity.
B. Heel effect: beam intensity is lower on the anode side (correct)
Correct. The anode side beam is weaker, so thicker parts go to the cathode side.
C. Inverse square law
The inverse square law concerns distance from the source, not the anode-cathode axis.
D. Grid cut-off
Grid cut-off is a grid alignment error and unrelated to anode angle.

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 B, Heel effect: beam intensity is lower on the anode side. X-rays emitted toward the anode side travel through more target material at the angled anode surface and are partly absorbed, so intensity is lower there.

Why is "Heel effect: beam intensity is lower on the cathode side" not the answer?

The cathode side has the higher, not lower, intensity.

Why is "Inverse square law" not the answer?

The inverse square law concerns distance from the source, not the anode-cathode axis.

Why is "Grid cut-off" not the answer?

Grid cut-off is a grid alignment error and unrelated to anode angle.

What concept does this question test?

It tests Imaging physics: anode heel effect in Radiology. The thicker or denser part is therefore placed under the cathode end, which has the stronger beam. The effect is more marked with small anode angles and short distances.

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: anode heel effect?

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.