[doctoring]

Usually not!

PET scans are limited in resolution when you get down to the sub-5 mm or so range due to scanner technology and fundamental limits of the physics of positron/electron annihilation & photon emission.

A typical MRI (i.e. alas, not what this article is describing) can usually resolve something at that size and identify characteristics like diffusion restriction or contrast enhancement which can confirm metastasis.

Also, in the brain, PET scans (at least the most common, FDG, which is based on glucose) are extremely limited in utility because of the baseline high glucose metabolism of the brain, which makes it hard to distinguish from the metabolic activity of a tumor.

[fluidcruft]

The flip-side of that is that PET is vastly multiple orders of magnitude far more sensitive than MRI. So while PET may not be able to localize as well as MRI, it can detect smaller things if the targeting of the radioisotope is good.

[lostlogin]

Maybe the state of play has changed, as we scan for this indication in MR, not PET.

Have you a link to something as my understanding is that small lesions are better found with MR?

Or is this a rule that applies to high end research work and hasn’t hit clinical practice yet? Maybe a limitation of the isotopes used clinically?