Imaging modalities and physics: F-18 half-life and distribution: 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: F-18 half-life and distribution

Sample item

F-18 FDG has a half-life of about 110 minutes. What is the practical consequence for PET centres?

AThe patient must stay isolated for several days after injectionBIt can be stored for weeks and used on demandCIt must be produced on site in a Mo-99 generatorDIt can be delivered from a regional cyclotron to centres within a few hours

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

The answer and the reasoning

D. It can be delivered from a regional cyclotron to centres within a few hours

F-18 is made in a cyclotron and the roughly 2 hour half-life lets it be transported to centres that have no cyclotron of their own. Shorter-lived tracers such as O-15 (2 minutes) must be made on site.

Option by option

A. The patient must stay isolated for several days after injection
Patients need only short, simple precautions because of the short half-life and low-energy photons.
B. It can be stored for weeks and used on demand
The activity falls by half every 110 minutes, so it cannot be stored for weeks.
C. It must be produced on site in a Mo-99 generator
F-18 is cyclotron-produced, and generators are used for Tc-99m, Rb-82 and Ga-68.
D. It can be delivered from a regional cyclotron to centres within a few hours (correct)
Correct. The half-life is long enough for transport by road within a few hours.

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 D, It can be delivered from a regional cyclotron to centres within a few hours. F-18 is made in a cyclotron and the roughly 2 hour half-life lets it be transported to centres that have no cyclotron of their own.

Why is "The patient must stay isolated for several days after injection" not the answer?

Patients need only short, simple precautions because of the short half-life and low-energy photons.

Why is "It can be stored for weeks and used on demand" not the answer?

The activity falls by half every 110 minutes, so it cannot be stored for weeks.

Why is "It must be produced on site in a Mo-99 generator" not the answer?

F-18 is cyclotron-produced, and generators are used for Tc-99m, Rb-82 and Ga-68.

What concept does this question test?

It tests Imaging modalities and physics: F-18 half-life and distribution in Radiology. Shorter-lived tracers such as O-15 (2 minutes) must be made on site.

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: F-18 half-life and distribution?

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.