Dear SPM users,
I am using the 'spm_read_vols' function to extract time-series information for my fMRI data but I do not understand the structure of the output completely. Below mentioned are some of my doubts.
I have a vector of multiple images which I give as an input to the command. I got my output in [Y,XYZ].
1. I have an understanding that Y here is a 4D matrix where the 4th dimension represents the intensity. But I am not sure of what does the first three dimensions represent? If they represent the coordinates then are these coordinates in mm or some other representation because I am not getting any negative values in these dimensions and I know that brain coordinates range from -r(-x,-y,-z) to r(x,y,z). If they are in some other representation then how can they be converted to mm.
2. If Y contains the coordinate values then what is XYZ variable for?
3. How can I get the intensity values from Y for some specific coordinate(in mm)?
Thanks and regards,
Mohit
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