Signa hdx 3.0t

In vitro MR imaging was carried out using a clinical 3.0 T MRI scanner (GE, Signa HDx 3.0T, USA) with a head coil. The Mn-IONPs@PEG and Mn-IONPs-TMAH (shown in SI) solutions with [Fe+Mn] concentrations from 0 to 0.5 mM were imaged using the following parameters: fast spin echo sequence (FSE) T₁WI: repetition time (TR) = 240 ms, echo time (TE) = 7.5 ms, field of view (FOV) = 160×160 mm², matrix = 320×192, slice thickness/spacing =2.0 mm/0.1 mm, number of excitations (NEX) = 4; T₁ mapping: TE = 9 ms, TR = 150, 300, 600, 900, 1200 ms, FOV = 160×160 mm², matrix = 256×256, slice thickness/spacing = 2.0 mm/0.1 mm, NEX = 1; FSE T₂WI: TR = 2000 ms, TE = 46.5 ms, FOV = 160×128 mm², matrix = 192×160, slice thickness/spacing = 2.0 mm/0.1 mm, NEX = 4; T₂ mapping: TR = 1500 ms, TE = 7.8, 15.6, 23.5, 31.3, 39.1, 46.9, 54.8, 62.6 ms, FOV = 160×128 mm², matrix = 160×128, slice thickness/spacing = 2.0 mm/0.4 mm, and NEX = 1.

MRI was performed using a Signa HDx 3.0 T (GE Healthcare), with an eight channel head coil and pneumatic driver. MR room temperature was similarly maintained at 20°C. A spin-echo echo planar imaging MRE sequence was used. Imaging parameters were as follows: TR=448 ms, TE=47.2 ms, field-of-view=19.2×19.2 cm², voxel size=3.0×3.0×3.0 mm³, imaging matrix=64×64, vibration and motion-sensitising gradient (MSG) frequency=125 Hz, MSG cycle=2, phase offset=4 and readout direction=R-L. MRE was carried out once for each phantom. The storage modulus was calculated using the three-dimensional integral-type reconstruction formula (ITRF)21 and spatiotemporal directional filtering.22 (link) Support size of the test function using ITRF was 3, 5 or 7, which was set to half of the propagation wave length.
Although the stiffness in MRE is usually reported as a complex shear modulus in kilopascals, we transformed the storage map to an SWS map using equation (5) for comparison between pSWE, MRE and a rheometer, with stiffness reported in metres per second. ROI size was set to 6×6 mm², approximating the ROI size of VTQ, containing four pixels each. ROI was set at 2.0, 3.0, 4.0, 5.0 and 6.0 cm depth from the passive pneumatic driver on the velocity map (figure 1). Mean and SD in each ROI were calculated.

In a typical measurement, the sample was dissolved in deionized water and diluted at an iron concentration range of 0–20 μg/mL. The samples were transferred to a 96-well plate, and T₂ relaxation time was determined by using a whole-body magnetic resonance (MR) scanner (SignaHDx 3.0T; GE Healthcare Bio-Sciences Corp., Piscataway, NJ, USA).

All MR images were acquired with a 3.0-T scanner (Signa HDx 3.0T; GE Healthcare, Milwaukee, WI, USA). RF transmission was performed using the body coil of the scanner. We used a circular, 3-cm diameter, receive-only surface coil (Takashima Seisakusho, Tokyo, Japan). The coil was encased (length, width, height: 126 × 50 × 15 mm), and a 21-mm aperture was created at the top and bottom of the case. The coil was the same type as that developed previously;⁷ however, it was not the same one as was used in a preclinical research, since we purchased another coil from Takashima Seisakusho for this clinical research. We made sure that we were able to safely preform MR scans using this coil based on the following results: the coil passed a standard voltage proof test and a standard test on RF-induced heating according to the American Society for Testing and Materials (ASTM) F2182-11a.