Dear FSL experts,
I'm having some trouble calculating the percent signal change (PSC) from perfusion fMRI data when using the perfusion subtraction approach and Featquery.
In FSL website (http://www.fmrib.ox.ac.uk/fsl/feat5/perfusion.html) it is stated that using the perfusion subtraction approach the Featquery will automatically output percent change values that correspond to 100*(perfusion signal change)/(perfusion baseline). However, if I analyse a perfusion fMRI dataset using the perfusion subtraction approach the PSC results don't make sense and don't match the PSC obtained with the full perfusion model.
Example, visual activation (PSC calculated in the same ROI):
Perfusion subtraction approach:
- PSC = 0.23%
Full perfusion model approach:
- COPE1 (perfusion activation) = 0,1296
- COPE5 ((perfusion baseline) = 0,3311
--> PSC = 100*COPE1/COPE5 ~ 40%
- COPE3 (BOLD effect) = 0.85%
Thanks for the attention.
Best regards,
Ines Sousa
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