Gyroscan

A 1.5 Tesla MRI scanner with an eight-channel phased array head and neck surface coil (Gyroscan; Philips, Best, Netherlands) was used. A time resolved 3D-PC MRI sequence was used, providing a 4D velocity field. Flow-encoding directions were head–foot, right–left, and anterior–posterior. A dynamic cine image of one cardiac cycle was created by imaging 32 phases per heartbeat (without interpolation), synchronized with the heartbeat. The imaging parameters were: repetition time, 9.8–16.4 ms; echo time, 6.6–6.7 ms; flip angle, 20°; field of view, 22 × 22 for females and 32 × 32 cm² for males; velocity encoding, 5 cm/s for volunteers, 30 cm/s for AD and iNPH patients; acquisition matrix, 1.96 × 1.96 × 1.96 mm³ (isotropic); sensitivity encoding factor of 2. Ten slices per volume were acquired, using 4–8 pixels to calculate the velocity and pressure gradient, and 12–20 pixels for the rotation. The acquisition time for this sequence was on average 32 min, depending on heart rate. The trigger for timing the 3D-PC was the peripheral pulse, measured from a finger.

MRI data were collected using a 3 Tesla whole body MRI scanner (Philips Gyroscan Achieva TX) using a 32-channel head coil, at the department of Radiology at MUMC+.
For the functional images, a T2^∗-weighted standard echo-planar imaging (EPI) sequence was used to acquire 40 axial slices (3 mm isotropic) covering the entire cortical volume, using the following parameters: repetition time (TR) = 2000 ms, echo time (TE) = 25 ms, flip angle = 75°, matrix size = 120 × 240, SENSE factor = 2. In total, 225 functional volumes were collected, of which the first two volumes were dummy volumes that were discarded from subsequent analysis to avoid T1 saturation effects.
T1-weighted anatomical images were acquired using a 3D turbo field echo (TFE) sequence with the following parameters: 170 slices, 1 mm isotropic, TR = 8.1 ms, TE = 3.7 ms, flip angle = 8°, matrix size = 240 × 240.

All MRI scans were performed with a standardized protocol at a central site on the same 1.5 T scanner (Gyroscan; Philips Medical Systems, Best, The Netherlands). The MRI scans were performed at least 30 days after intravenous high dose steroids and not more than 120 days after or before their respective spinal tap (Figure 2). Axial brain acquisitions included fluid attenuated inversion recovery (FLAIR) and 3D T1-weighted images (3D-T1W). Image analyses included the analyses of changes in T2 lesions and whole brain volumes. Absolute T2 lesion volumes and brain parenchymal fractions were obtained using ScanView software [24 (link)] and percent changes in whole brain (WB) volumes were obtained using the SIENA method [25 (link),26 (link)]. Lesion filling on 3D T1-WI images was used to reduce the impact of T1 hypo-intensities on tissue segmentation [27 (link)].

All subjects underwent a fetal MRI examination for diagnostic purposes and were imaged on a 1.5 T(esla) Philips Achieva MR system (Philips Gyroscan, Best, The Netherlands) using a five-channel phased-array cardiac coil, adjusted to the position of the fetal head. In addition to the standard diagnostic protocol, an echo planar diffusion tensor sequence (repetition time TR = 2260msec, echo time TE = 90msec, b-values of 0 and 700sec/mm²), using 16 gradient-encoding directions, was acquired in an axial plane perpendicular to the axis of the brainstem. Fifteen slices were recorded during an overall imaging time of 1:16 minutes of scanning. The acquired voxel size of 2.14(axial)/2.19(sagittal)/3(slice thickness)mm was reconstructed to 0.94/0.94/3mm using an imaging matrix of 256. The specific absorption rate (SAR) did not exceed 11%/0.4W/kg, and thus, was within current safety recommendations [38 , 39 (link)]. Generally, fetal DTI sequences in non-sedated fetuses were only acquired if fetal motion during acquisition of preceding structural sequences did not exceed certain (acceptable) limits. Standardized axial T2-w sequences (TR = 8828msec, TE = 140msec), with a voxel size of 0.75/0.75/3mm, or steady state free precession sequences (SSFP) (TR = 3.2msec, TE = 1.62msec) were acquired as anatomical references for tractography.

In all subjects, brain MRI was acquired at the University of Siena on a 1.5-T Philips Gyroscan (Philips Medical Systems, Best, Netherlands). A sagittal survey image was used to identify the anterior and posterior commissures. Sequences were acquired in the axial plane parallel to the commissural line. A FLAIR (fluid attenuated inversion recovery) image [repetition time (TR) = 9000 ms, echo time (TE) = 150 ms, inversion recovery delay = 2725 ms, voxel size = 1 × 1 × 3 mm] was acquired for the assessment of WM hyperintensities. DTI (diffusion tensor imaging) data consisted of echo-planar imaging (EPI) (TR = 8500 ms; TE = 100 ms; voxel size = 2.5 mm³), with diffusion weighting distributed in 32 directions and b-value = 1000 s mm^–2. Resting-functional MRI (FMRI) data were 190 volumes of EPI sequence with TR = 1000 ms, TE = 50 ms, voxel size = 3.75 × 3.75 × 6 mm. A high-resolution T1-weighted image (TR = 25 ms, TE = 4.6 ms, voxel size = 1 mm³) was acquired for image registration, anatomical mapping, and analysis of gray matter (GM) volume.