Achieva tx series mri system

T1-weighted imaging and diffusion imaging data were obtained using the same protocol at either the Aberdeen study site (3T Philips Achieva TX-series MRI system Philips Healthcare, Best, the Netherlands) or the Dundee study site (Siemens 3T Prisma-FIT Siemens, Erlangen, Germany). T1 scans were processed using FreeSurfer 5.3.0 and the Desikan–Killiany atlas [22 (link)] was used for subcortical segmentation and cortical parcellation. FA and MD for white matter tracts were derived using TBSS toolkit within FSL following the ENIGMA DTI analysis protocol (http://enigma.ini.usc.edu/protocols/dti-protocols/). The John Hopkins University white matter atlas [23 (link)] was used to define white matter tracts. Full details on image acquisition and quality control measures are described in the Supplementary Materials and elsewhere [20 (link), 24 (link), 25 (link)].

Participants were scanned at two centers: the Ninewells Hospital in Dundee and at the Aberdeen Royal Infirmary in Aberdeen. Participants in Dundee were scanned using a Siemens 3T Prisma‐FIT (Siemens Healthineers) with a 20‐channel head and neck coil and a back‐facing mirror (software version VE11, gradient with max amplitude 80 mT/m and maximum slew rate 200 T/m/s). In Aberdeen, participants were imaged on a 3 T Philips Achieva TX series MRI system (Philips Healthcare) with a 32‐channel phased‐array head coil with a back‐facing mirror (software version 5.1.7; gradients with maximum amplitude 80 mT/m and maximum slew rate 100). Both study centers followed the same protocol including structural sequences.¹⁷ 3T MRI scans were anonymized at the time of acquisition and scanning site was included as a covariate in statistical analyses. Full details of the imaging sequences and parameters are published elsewhere.¹⁹