Nuclear medicine: reducing MAA particles: 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.

Try it

Radiology · Nuclear medicine: reducing MAA particles

Sample item

A patient with a known right-to-left cardiac shunt needs a lung perfusion scan. What adjustment is made to the Tc-99m macroaggregated albumin dose?

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

The answer and the reasoning

D. Reduce the number of particles injected, since some bypass the lungs and lodge in systemic capillaries

Macroaggregates normally lodge in pulmonary capillaries, but in a right-to-left shunt they reach the brain and kidneys. Fewer particles limit systemic embolisation, and the same precaution applies in severe pulmonary hypertension. Uptake outside the lungs on images also quantifies the shunt.

Option by option

  • A. No change is needed in any shunt

    Particle number is adjusted in shunts and pulmonary hypertension.

  • B. Replace MAA with colloid

    Colloid is not used for lung perfusion imaging.

  • C. Increase the number of particles for better counts

    More particles would increase systemic capillary blockade.

  • D. Reduce the number of particles injected, since some bypass the lungs and lodge in systemic capillaries (correct)

    Correct. Fewer particles reduce the risk of systemic embolisation.

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 D, Reduce the number of particles injected, since some bypass the lungs and lodge in systemic capillaries. Macroaggregates normally lodge in pulmonary capillaries, but in a right-to-left shunt they reach the brain and kidneys.

Why is "No change is needed in any shunt" not the answer?

Particle number is adjusted in shunts and pulmonary hypertension.

Why is "Replace MAA with colloid" not the answer?

Colloid is not used for lung perfusion imaging.

Why is "Increase the number of particles for better counts" not the answer?

More particles would increase systemic capillary blockade.

What concept does this question test?

It tests Nuclear medicine: reducing MAA particles in Radiology. Fewer particles limit systemic embolisation, and the same precaution applies in severe pulmonary hypertension. Uptake outside the lungs on images also quantifies the shunt.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Nuclear medicine: reducing MAA particles?

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.