1.5 t mri scanner

All subjects had an estimation of intrahepatic triglyceride (IHTG) percent by magnetic resonance imaging (MRI) at baseline and final visits. Specifically, a multi-echo multi-slice gradient-echo pulse was used to acquire in/out of phase images of the whole liver using a 1.5T MRI scanner (Philips Healthcare, Best, The Netherlands). MRI method was chosen over conventional magnetic resonance spectroscopy (MRS) because MRI in principle uses the same method (Dixon method) as MRS, but can provide an evaluation of the fat concentration of the whole liver (other than one single imaging voxel by MRS that also has to be manually placed), which would be preferred for this longitudinal study. In addition, studies have shown close agreement between MRI and MRS measurements of fat fraction in children with known or suspected NAFLD (29 (link)). The triple-echo method was used to control/reduce the confounding effects of intrinsic T2/T1 relaxation in the liver fat quantification (30 (link), 31 (link)).

The volunteers were imaged on a 1.5 T MRI scanner (Philips Achieva) using the inbuilt body coil. Precontrast sequences included 4 axial 3-dimensional T1-weighted images at variable flip angles (2, 10, 20, and 30 degrees) for T1 quantification and had the same parameter settings as the dynamic MR sequence, except for the flip angle. Dynamic contrast-enhanced MRI data were acquired for 50 minutes at a temporal resolution of 6.2 seconds and a flip angle of 20 degrees, with a 3-dimensional RF-spoiled gradient-echo sequence (T1 fast field echo). The imaging parameters for both were as follows: 48 axial slices; voxel size, 2.1 × 2.1 × 4 mm; reconstruction matrix, 176 × 176; 3 milliseconds repetition time; 0.68 millisecond echo time; 88 phase encoding steps; 62% sampling; partial Fourier; and Fourier interpolation. Two minutes after the start of the DCE acquisition, a bolus of gadoxetate (Primovist; Bayer, Leverkusen, Germany) at a clinically relevant dose of 0.025 mmol/kg (ie, 0.1 mL/kg) was administered at 2 mL/s and flushed with 20 mL of saline at the same rate.

All fetal brain MRI scans were performed using a Philips 1.5 T MRI scanner with a 16-channel Sense XL Torso Coil. The imaging sequences included steady-state free-precession (SSFP), single-shot turbo spin echo (SSTSE), T1-weighted fast imaging (T1WI), and DWI. DWI sequence was performed in the transverse plane using b values of 0 and 700 mm²s⁻¹. The maximal b value of 700 was chosen to increase the signal-to-noise ratio (SNR) of the immature brain for demonstrating optimal contrast in the fetal brain. The following parameters were used: repetition time (TR), 2,494 ms; echo time (TE), 96 ms; slice thickness, 4 mm; field of view (FOV), 280 mm² × 320 mm²; matrix, 188 × 125; spacing, 0 mm; flip-angle, 90°. The scan time of the DWI sequence was 60 s. The overall duration of fetal MRI acquisition ranged from 15 to 25 min.
Pregnant women were lying in the supine position or the left side position. Neither the mother nor the fetus took sedatives during the examinations. Firstly, the middle and lower abdomens of pregnant women were scanned in the coronal plane, followed by a focused multiplanar scan of the fetal brain. Subsequently, the fetal chest, abdomen, and pelvis were scanned in the axial, sagittal, and coronal planes, respectively.