Dear SPM/VBM experts,
I have a few questions regarding volume extraction of VBM8 data using ROIs. Specifically, we have been using VBM8 and would like to extract volume information from m0wrp (modulated, non-linear only, dartel warped, segmented) GM and WM images.
1) If one is concerned primarily with quantifying GM or WM atrophy, would it be best to extract the voxel count, mean or some other measure (e.g. eigenvariates?) from VBM data using an ROI approach?
2) In comparing some of the ROI extraction functions, there seems to be discrepancy between whether one should exclude NaN voxels when computing the ROI mean (e.g. the REX program) or convert NaN voxels to 0 and include them when calculating the ROI mean (e.g. WFU_pickatlas' 'Generate Table' function). Does anyone have any insight into the pros/cons of each approach and/or examples of when it would be appropriate to use each?
Any insight or discussion would be greatly appreciated!
Thanks,
Doug Merkitch
Neurological Sciences
Rush University Medical Center
Phone: (312) 563-3853
Fax: (312) 563-4660
Email: [log in to unmask]
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