Signa architect

All subjects underwent MR exams in the supine position on a 3.0 T whole-body scanner (SIGNA Architect, GE Healthcare, Milwaukee, United States) using a 19 channel high-resolution head and neck coil. All subjects were instructed not to move and swallow during scanning to minimize motion artifacts. Routine sequences were acquired, including Sagittal T2WI FSE (TR:2000 ms, TE:102.0 ms, NEX:1.00, Thickness:3.0, Spacing: 0.5), Sagittal FS (Fat Saturation) T2WI FSE (TR:2816 ms, TE:102.0 ms, NEX:2.00, Thickness:3.0, Spacing: 0.5), Sagittal T1WI FSE (TR:612 ms, TE:10.0 ms, NEX:2.00, Thickness:3.0, Spacing: 0.5). Synthetic MRI (MAGiC, MAGnetic resonance image Compilation) scan of the spinal cord was performed at 0.5 mm in-plane resolution and 4 mm slice thickness in multiple axial sections perpendicular to the spinal cord. Other imaging parameters for MAGiC were as follows: TR: 4008 ms, TE: 29.3 ms, spacing: 1.0mm, Matrix size: 400 × 400, NEX: 1.00, scanning time: 7min45s.

The r₁ and r₂ relaxivities of SPIO@PEG-GdDTPA were measured on a 1.5 T clinical MRI scanner system (μMR 588, United Imaging Healthcare) and a 3.0 T clinical MRI scanner system (Signa Architect, GE Medical systems) using the head RF coils. The samples were dispersed in deionized water with different paramagnetic metal ion concentrations at 0.5, 0.4, 0.3, 0.25, 0.15, 0.1, 0.06 and 0.03 (Fe + Gd) mM. Subsequently, longitudinal and transverse relaxation rates (the reciprocal of relaxation times) were, respectively, measured and used for calculating corresponding relaxivity by seeking the slopes of best fit lines of relaxation rates versus metal ion concentrations. T₁- and T₂-weighted MR images in vitro were acquired with a conventional SE sequence by the following parameters: T₁-weighted images at 1.5 T (TE = 12.2 ms, TR = 125 ms, slice thickness = 3 mm, field of view = 200 × 120 mm, flip angle = 90°); T₂-weighted images at 1.5 T (TE = 18 ms, TR = 3500 ms, slice thickness = 3 mm, field of view = 200 × 120 mm, flip angle = 90°).

MRI examinations of all participants were performed on a 3.0-Tesla MRI scanner (Signa Architect, GE Healthcare, Milwaukee, WI, United States) equipped with a 48-channel phased-array head coil. In order to reduce noise and minimize head movement, earplugs were used, as well as tight foam padding.
DKI data were obtained using a single-shot spin echo planar imaging (EPI) sequence with the following parameters: diffusion encoding was applied in 60 directions with two b values (b = 1,000 and 2000 s/mm²) and one non-diffusion weighted image (b = 0 s/mm²), flip angle (FA) = 90^o, repetition time (TR) = 8,819 ms, echo time (TE) = 90.4 ms, field of view (FOV) = 240 mm × 240 mm, matrix = 120 × 120, NEX = 1, voxel size = 2 mm × 2 mm × 2 mm, slice gap = 0 mm, 75 axial slices, the total acquisition time was 9 min 7 s. Anatomical 3D gradient-echo T1-weighted images were obtained using a 3D gradient-echo sequence to obtain a high-resolution volume image (FA = 12^o, TE = 3.0 ms, TR = 7.4 ms, FOV = 240 mm × 240 mm, matrix = 240 × 240, slice thickness = 1.0 mm without gap, sagittal slices = 166, scan time = 3 min 47 s).

All examinations were performed on a 3T MR imaging system (Signa Architect, GE Healthcare, Milwaukee, WI, USA) with a 48-channel head coil. 4D flow MRI was performed with non-contrast technique. MRI sequences included intracranial time of flight MRA and 4D flow MRI. Imaging parameters for 4D flow MRI were the following: FOV = 200 × 200 mm², TR/TE = 5.5/2.9 ms, VENC = 80–100 cm/s, flip angle = 8°, bandwidth = 50 kHz, matrix = 200 × 200, number of slabs = 80, spatial resolution for the composite image = 0.5 × 0.5 × 1 cm³. Retrospective cardiac gating with electrocardiogram was acquired for 4D flow MRI. The 20 time-frames per heartbeat resulted in a temporal resolution that varied from 42 to 56 ms depending on the patient’s heart rate. Consequently, total acquisition times were between 10 and 12 min.

MR images were obtained using a commercial 3T scanner (Signa Architect, GE Healthcare, Milwaukee, WI, USA). ZTE imaging is performed as part of routine chest MRI protocol at our institution (Gyeongsang University Changwon Hospital, Changwon, Korea). Two sets of ZTE lung MR imaging were obtained using 16-channel CAA (ZTE-CAA) and 30-channel AIR coils (ZTE-AIR), respectively, combined with a 40-channel posterior array coil. The order of the two ZTE scanning was random for each patient.
Scans were performed during quiet breathing. Signals of respiratory bellows wrapped around the patient’s upper abdomen were used as surrogates of respiratory motion. Data were prospectively acquired when the position of the diaphragm was within an acceptance window during approximately one-third of the end-expiration phase. Coronal images with isotropic resolution of 1.5 mm were obtained. Original coronal image data were reformatted into axial images. ZTE scan parameters in both scans were as follows: repetition time, 393~503 ms; echo time (ΔT), 16 μs; flip angle, 2°; No. of spokes per segment, 256; field of view, 384 × 384 mm²; receiver bandwidth, ±31.25 kHz; respiration trigger window, 30% of respiratory cycle; and mean scan time, 137 s (127–148 s).

Dynamic contrast-enhanced breast MRI examinations were performed with a 3.0-T or 1.5-T system (SIGNA Architect, GE Healthcare, Milwaukee, USA or Avanto, Siemens, Germany) and a dedicated 16-channel or 4-channel SENSE breast coil, with the patient in the prone position. Firstly, unenhanced T2-weighted propeller short T1 inversion recovery (STIR) or turbo inversion recovery magnitude (TIRM) axial images and T1-weighted spin echo axial images were obtained, and then 0.1 mmol/kg gadoteridol (15 mL ProHance; Bracco imaging, Singen, Germany) was administrated via intravenous injection. Dynamic contrast-enhanced examinations included one pre-contrast and four post-contrast bilateral axial image acquisitions using a fat-suppressed T1-weighted 3D fast field echo sequence (TR/TE;7.0/1.7 300 × 280 matrixes, field of view; 360 × 360 mm, slice thickness; 2 mm, no gap for 3.0-T, TR/TE; 4.8/2.4, 384 × 338 matrixes, field of view; 380 × 380 mm, slice thickness; 1 mm, no gap for 1.5-T). Four post-contrast image series were obtained at 90, 180, 270, 360 s after contrast administration. In all studies, dynamic subtraction (i.e., post-contrast images minus precontrast images) and 3D maximum intensity projection images were generated. The approximate total time per examination was 30 min.

Fourier transform infrared (FTIR) spectra were delineated on a Perkin-Elmer spectrophotometer in the region of 4000–400 cm⁻¹ with a powder sample on a KBr plate. X-ray diffraction (XRD) patterns were collected on a Dandong Fangyuan DX-1000 diffractometer (Haoyuan Instrument, China) with a Cu Kα radiation source (λ = 1.5418 Å) in the 2θ range 20–80^°. Thermogravimetric analysis of all samples was performed on NETZSCH TG209F1 Thermogravimetric Analyzer (NETZSCH Scientific Instruments Trading Ltd, Germany). Elemental analyses were performed by energy-dispersive spectrometer (EDS) on INCAPentaFETx3 (Oxford Instruments, UK). The size distribution and morphology of all samples were investigated by TEM (Tecnai G2 F20 S-TWIN, FEI), for which 10 µl of the samples were dried on a copper grid. The hydration diameter and zeta potential of all samples were tested by DLS on a Malvern Nanosizer (Zetasizer Nano ZS, UK). Iron and gadolinium concentration of all samples were evaluated by elemental analysis using an atomic absorption spectroscopy (AA800, Perkin-Elmer, USA). T₁ and T₂ relaxivities were recorded and calculated on a 1.5 T (μMR 588, United Imaging Healthcare, PRC) and 3.0 T clinical MRI scanner (Signa Architect, GE Medical systems, USA) at room temperature.