I have to compare the extent of the activation for a same task in a subject acquired at intervals of months. To be sure that the changings I observe (i.e. the different values of the correlation coefficients estimated with FIM in the various voxels) are due to the modified conditions of the subject, and not to different different noise levels, I want to estimate the noise levels (at each voxel?) in the different acquisitions (3D+time datasets) and check if they are equal or not.
Any suggestion on how to perform that?
Thank you,
Davide
