Avanto 1.5 t scanners

High-resolution T1-weighted structural MRI scans (MPRAGE) were collected on Siemens Avanto 1.5 T scanners across five Australian research sites (Loughland et al., 2010 (link)). 176 contiguous 1 mm sagittal slices were collected (field-of-view 250 × 250 mm², time-to-repetition 1980 ms, time-to-echo 4.3 ms, data acquisition matrix 256 × 256, voxel size 0.98 × 0.98 × 1.0 mm³, flip angle 15°). Scans were individually reviewed for motion and other artefacts. The VBM8 toolbox for SPM8 (http://dbm.neuro.uni-jena.de/vbm/) was used for image pre-processing. Images were segmented into grey matter, white matter and cerebrospinal fluid using a unified segmentation approach combined with Hidden Markov Random Fields to improve signal-to-noise ratio. Images were subsequently normalized and modulated with the Jacobian determinants of the deformation parameters in order to preserve the absolute tissue volumes. Modulation of non-linear effects without affine normalization allows interpretation of relative volumes, negating the need to further account for total individual brain volume. No spatial smoothing was applied (Klöppel et al., 2008 (link); Chu et al., 2012 (link)).