1.5t scanner

All MRI scans were performed at the Department of Radiology at International St. Mary’s Hospital. LS-MRI examinations were performed using a 3T Avanto (Siemens Medical Systems, Erlangen, Germany) or with 1.5 T scanners (Philips Medical Systems, Best, Netherlands). For LS-MRI examinations, axial turbo spin echo T2-weighted images were obtained with a slice thickness < 4.0 mm, 0.9 mm intersection gap, 3937-ms/120-ms repetition time/echo time, 150 × 150 field of view, 256 × 250 matrix. All LS-MRI data were transferred from the MRI unit to an INFINITT Picture Archiving System (INFINITT Medical Systems, Seoul, Korea).

Structural T1‐weighted magnetic resonance imaging (MRI) scans were acquired on either GE, Siemens, or Philips 1.5T scanners at various ADNI sites using standardized MRI acquisition protocols described in detail elsewhere.²⁸Anatomical scans (baseline and follow‐up measures) were processed using the FreeSurfer software (version 4.3)²⁹ to obtain regional brain volume measures. This atlas‐based approach was previously described and validated.³⁰ Right and left hemisphere hippocampal volumes were extracted from the ADNI database and the sum included into our analysis. To investigate whether effects were specific to the hippocampus, or could also be found in other brain regions,¹³ we assessed the following cortical volumes in follow‐up analyses: entorhinal, fusiform, lateral, and medial orbitofrontal, and middle temporal regions (bilateral), which were downloaded and calculated as above. Brain region volumes were adjusted for baseline total intracranial volume (ICV) by calculating the ratio between regional brain volume and ICV, multiplied by the overall sample mean of ICV.

Cardiovascular magnetic resonance data were acquired using one of two 1.5 T scanners (Philips Achieva, Best, the Netherlands, between 2003 and 2015, and Siemens MAGNETOM Aera, Erlangen, Germany, between 2015 and 2017). Standard ECG‐gated short‐axis and long‐axis cine balanced steady‐state free precession images covering the heart were acquired at end‐expiratory breath‐hold using a cardiac phased‐array coil either in combination with a second cardiac phased‐array coil (Philips) or in combination with a spine phased‐array coil (Siemens). Typical image parameters were 1.4 × 1.4 × 8 mm³, flip angle 60°, TR/TE 3/1.4 ms, with an acquired temporal resolution of 50 ms reconstructed to 30 (Philips) or 25 (Siemens) time frames per cardiac cycle. A standard 2D gradient recalled echo with retrospective ECG‐gating was used to acquire phase‐contrast quantitative flow data in the pulmonary artery during free breathing. Typical parameters were 1.3 × 1.3 × 8 mm³, TR/TE 20/3 ms, flip angle 10°/20°. Acquisition time was approximately 2 min averaged to 30 or 35 phases per cardiac cycle (<30 ms per phase). If arrhythmia was present, real‐time phase‐contrast flow sequences over 5 s were acquired. Typical parameters were 3 × 3 × 9 mm³, TR/TE 5/5 ms, flip angle 15°. Velocity encoding was set to 150–250 cm/s on an individual basis.