Hi chin,
This was not a silly question. Interest in PET is never silly ;-)
The raw PET-signal is radioactivity concentration at a given point in
space and time. There are a lot of different radioactive compounds
and a lot of different ways how to convert measured radioactivity
concentration into resulting ROI- or voxel-values.
I assume you refer to PET perfusion studies, e.g. with 15O water.
Here people calculate a voxel-value more or less proportional to
perfusion (or a perfusion ratio, as compared to a reference tissue).
When PET people talk about perfusion they mean [ml blood] / ([ml
brain tissue][min]). Many people talk about K1, which is perfusion
times extraction fraction.
Hope that helps,
Matthias Reimold
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