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Dear all,
I want to extract the individual voxel-wise beta values within a pre-defined ROI, let's say a sphere centered at some point (x0,y0,z0). I understand that Marsbar is able to extract the ROI-mean beta value (I assume the avearge of all the betas in that particular region) but I want to obtain the voxel-wise betas of that region.
The first thought is to read the beta.img and get whatever I want but the problem is that I cannot find the correspondence between the MNI coordinates and the matrix subscripts. Besides, the beta matrix contains NaNs (Not a number) I do not know how to interprete.
So my questions are as follows:
1) How can I obtain the voxel-wise betas in a pre-defined ROI?
2) Can I regard the NaNs simple as zeros?
Any comments and advice will be greatly appreciated.
Many thanks and best regards,
Ce
