Intera mr scanner

The participants were scanned in a 1.5T Phillips Intera MR scanner. Diffusion-weighted images were obtained using a single-shot SE-EPI sequence with TE/TR = 79/11,663 ms, SENSE acceleration factor 2, FOV 252 X 252 mm, and in-plane resolution 2.25 X 2.25 mm² in 70 axial slices (slice thickness of 2.25 mm). Diffusion gradients were applied in 15 directions with b = 1,000 s/mm², and a volume without diffusion weighting was acquired. Two common DTI metrics were assessed: fractional anisotropy (FA), which denotes the strength of diffusion directionality, and mean diffusivity MD, which indicates the overall rate of diffusivity (Madden and Parks, 2017 ). In aging, a decrement in FA has been reported, which often is coupled with an increment in MD (de Groot et al., 2016 (link)). These events suggest degeneration in white matter in terms of tissue loss and replacement of the damaged tissue by free water (Pfefferbaum and Sullivan, 2003 (link)). Of interest for the present study is that the magnitude of FA and MD changes is reported to be greater in AD than in normal aging (Caballero et al., 2018 (link)).

All participants were scanned using a 1.5 T Philips Intera MR scanner. During scanning, foam pads were used to reduce head motion and scanner noise. Diffusion-weighted images were obtained using a single-shot echo-planar imaging sequence according to the following parameters: repetition time (TR) = 11,000 ms; echo time (TE) = 71.6 ms; field of view (FOV) = 230 × 230 mm; matrix size = 144 × 144; voxel dimensions = 1.6 × 1.6 × 2 mm; slice thickness = 2 mm; 32 non-collinear diffusion directions with a b-value of 800 s/mm² and one additional volume without diffusion weighting (b = 0 s/mm²); and 73 transverse slices without gaps, covering the entire brain. We also acquired high-resolution 3D brain anatomical images using a T1-weighted MP-RAGE sequence according to the following parameters: TR = 25 ms, TE = 4.6 ms, FOV = 240 × 240 mm, matrix size = 256 × 256, and 140 contiguous axial slices with slice thickness = 1 mm.

Neuroimaging data were acquired using a 3T Philips Intera MR-scanner (Best, the Netherlands), equipped with a SENSE 32-channel head coil. Functional images were acquired using a T2*-weighted echo-planar sequence and consisted of 39 descending axial slices, 3 mm thick, and no slice gap (repetition time = 2 s; echo time = 30 ms; flip angle = 90°; FOV = 192 × 192 × 117 mm, with an inplane matrix consisting of 64 × 61 voxels at 3 × 3 × 3 mm). All scans were oriented 10–20° to the AC-PC transverse plane to prevent artefacts from nasal cavities. The task consisted of 275 functional volumes. In addition, a high-resolution anatomical T1 image was recorded using the following parameter settings: voxel size 1 × 1 × 1 mm; 170 slices; TR = 9 ms; TE = 3.5 ms; slice thickness = 1 mm; 256 × 256 matrix; FOV 256 × 232 × 170 mm.