Ingenia 3 t system

At both sites, MR data were initially acquired on identical Philips Achieva 3 T TX systems (Philips, Best, Netherlands), using 8-channel SENSE head coils. Due to a scanner upgrade, Bonn had to switch to a complementary Philips Ingenia 3 T system after n = 15 participants, while Munich had to do the same switch after n = 105 participants (Supplementary Table 1). Yet, the identical sequence parameters were used on all scanners. To account for possible confounds introduced by the scanner-specific differences, all second-level functional data analyses included dummy regressors for scanner identity as covariates of no interest.
During each run, 215 T2*-weighted EPI volumes were acquired (TR = 2000 ms, TE = 35 ms, flip angle = 82°, parallel imaging with SENSE = 2 (A − P); 32 interleaved oblique axial slices with a slice thickness = 4 mm (no gap); field of view = 220 × 220 × 128 mm; reconstruction matrix = 96 × 96; reconstructed voxel size = 2.29 × 2.29 × 4 mm). Five additional dummy scans were acquired (to achieve longitudinal magnetization equilibrium), but were already discarded before image reconstruction. For image registration purposes, high-resolution T1-weighted 3D-MPRAGE volumes were acquired (TI = 1300 ms, TR = 7.7 ms, TE = 3.9 ms, flip angle = 15°; 180 sagittal slices, field of view: 256 × 256 mm, reconstructed voxel size = 1³ mm³).

At both sites, Bonn and Munich, MRI data acquisition was performed on Philips Achieva 3 T TX systems or Philips Ingenia 3 T system using an 8‐channel SENSE head coil. Subject distribution among scanners: Bonn Achieva 3 T: 5 VP/VLBW, 12 FT, Bonn Ingenia 3 T: 33 VP/VLBW, 17 FT, Munich Achieva 3 T: 60 VP/VLBW, 65 FT, Munich Ingenia 3 T: 3 VP/VLBW, 17 FT. To account for possible confounds by scanner differences, functional and structural data analyses included scanner dummy‐variables as covariates of no interest. Across all scanners, sequence parameters were kept identical. Scanners were checked regularly to provide optimal scanning conditions and MRI physicists at the University Hospital Bonn and Klinikum rechts der Isar regularly scanned imaging phantoms, to ensure within‐scanner signal stability over time. Signal‐to‐noise ratio was not significantly different between scanners (one‐way analysis of variance with factor “scanner‐ID” [Bonn 1, Bonn 2, Munich 1, Munich 2]; F(3,182) = 1.84, p = .11). A high‐resolution T1‐weighted 3D‐MPRAGE sequence (TI = 1,300 ms, TR = 7.7 ms, TE = 3.9 ms, flip angle = 15°; 180 sagittal slices, FOV = 256 × 256 × 180 mm, reconstruction matrix = 256 × 256; reconstructed isotropic voxel size = 1 mm³) was acquired. All images were visually inspected for artifacts and passed homogeneity control implemented in the CAT12 toolbox (Gaser & Dahnke, 2016).

Nineteen subjects (10 ALS, 9 HCs) were imaged on a Philips Achieva 3T system (Best, Netherlands) using an 8-channel receive head coil. Forty subjects (19 ALS, 21 HCs) were imaged on a Philips Ingenia 3T system (Best, Netherlands) using a 15-channel receive head coil. Whole brain diffusion-weighted imaging was obtained using a multiple shot spin-echo technique (repetition time/echo time = 7075/62 msec, field of view 112 mm, 2-mm isotropic resolution, b values = 0, 800 sec/mm², 15 isotropically distributed gradients). ExploreDTI v4.8.2 (Utrecht, the Netherlands) was used to perform the data processing with incorporating a motion and eddy current correction algorithm. Seed regions of interest were placed in the posterior limb of the internal capsule and pons using detailed white matter atlases to generate the fiber tracks using standard deterministic stream.23 The fractional anisotropy (FA) values for the right and left corticospinal tract were calculated and averaged. Figure1 depicts the fiber tracking of the corticospinal tracts as well as the MRS voxel placement in the left MC and resulting spectra.