Dear SPM experts,
I’d like to perform VBM analysis on my structural data. I extracted an average grey matter volume value in a specified ROI using REX toolbox, derived from the segmented, modulated, warped, unsmoothed c1-image (smwc1…; all steps performed by low-dimensional SPM preprosessing pipeline as I rely on age-specific TPMs). I end with a value between 0 and 1 (which should be “volume” units as I rely on the modulated image). I know that I have to take into account the size of the ROI. What is not completely clear to me is: Do I have to multiply the extracted value by the voxel count (number of voxels within the ROI) or with the ROI’s volume (i.e., in mm^3) to get the final grey matter volume value for this ROI?
Thanks for any help.
Best, Sandra
|