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Dear experts,

I report an answer you gave about some negative values avatar partial volume correction:

"[...] Usually this only happens in small ROIs and/or low uptake regions. Why might the model not be perfect? It could be a number of things:

1. the MRI-PET registration is inaccurate 2. the MRI segmentation is inaccurate

3. the ideal segmentation is not reflected by the MRI segmentation (eg, one of the segmentations has a hot spot)"

I wonder if it is possible for you to give me an hint about the reason why an inaccurate registration or segmentation can cause negative uptake values. At first sight it seemed intuitive to me, but on second thought that's not so obvious.

I would be very grateful for any help!

Federica Di Antonio