CT: bolus tracking: 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 · CT: bolus tracking

Sample item

In CT angiography of the aorta, why is bolus tracking used?

AThe scan is triggered automatically when contrast in a chosen region of interest reaches a set attenuation thresholdBTo remove the need for intravenous contrastCTo increase the pitchDTo reduce the radiation dose to zero

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

The answer and the reasoning

A. The scan is triggered automatically when contrast in a chosen region of interest reaches a set attenuation threshold

Circulation time varies between patients, so a fixed delay can miss peak enhancement. A region of interest in the aorta is monitored and the acquisition starts when it reaches a preset Hounsfield threshold. This gives optimal vascular opacification.

Option by option

A. The scan is triggered automatically when contrast in a chosen region of interest reaches a set attenuation threshold (correct)
Correct. Triggering occurs on reaching threshold enhancement.
B. To remove the need for intravenous contrast
Contrast is still required.
C. To increase the pitch
Pitch is a separate scanning parameter.
D. To reduce the radiation dose to zero
Dose is not eliminated by tracking.

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 A, The scan is triggered automatically when contrast in a chosen region of interest reaches a set attenuation threshold. Circulation time varies between patients, so a fixed delay can miss peak enhancement.

Why is "To remove the need for intravenous contrast" not the answer?

Contrast is still required.

Why is "To increase the pitch" not the answer?

Pitch is a separate scanning parameter.

Why is "To reduce the radiation dose to zero" not the answer?

Dose is not eliminated by tracking.

What concept does this question test?

It tests CT: bolus tracking in Radiology. A region of interest in the aorta is monitored and the acquisition starts when it reaches a preset Hounsfield threshold. This gives optimal vascular opacification.

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 CT: bolus tracking?

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.