A 0 value usually indicates a bad or uninterpretable voxel which you would not want to include in your analysis. You can, of course, by not pruning. But I think you need to answer the question as to why the values are 0. Is 0 interpretable in this case?

On 1/11/2021 6:15 PM, Julie Ottoy wrote:

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Dear Doug,

I was wondering why the flag --prune is recommended (petsurfer website) when creating a stacked pet file and during surface-smoothing. If I understood correctly, this would set all vertices that are 0 in at least one subject to 0 ("set vox to 0 unless all frames are non-zero")? In my non-pvc data, it seems as though a lot of the surface-projected values are 0. Hence, when I perform a surface-based regression between PET and a regressor and I use the --prune flag during mri_concat, I don't get any results.

Thank you!

best regards

Julie
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