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Hello SPMers, We have a cohort of subjects consisting of both MPRAGE and IRFSPGR T1 structural images. We noticed that the IRFSPGR scans are visibly brighter (higher intensity) than the MPRAGE scans. We are looking at gray matter differences in VBM8 (modulated, non-linear only - i.e. "m0wrp1") between several groups, with all but 1 group having majority MPRAGE scans. My questions are: 1. Could these intensity differences bias our analyses or does VBM8 somehow account for the intensity differences BETWEEN scan type (i.e. not intensity differences within a single scan)? 2. If the answer to #1 is no, how could we go about correcting for scan type? Our current practice is to use scan type as a covariate in our SPM analyses. Any thoughts or recommendations would be greatly appreciated! -Doug Doug Merkitch Neurological Sciences Rush University Medical Center Phone: (312) 563-3853 Fax: (312) 563-4660 Email: [log in to unmask]