EDS measurements were carried out in low vacuum mode under a pressure of 50 Pa and accelerating voltage of 20 25 kV, working distance —10 mm, acquisition time from 35 to 100 s.
Small field of view T2: fast spin echo, flip angle = 125°, slice thickness = 4.5 mm, number of slices per acquisition = 27, TE/TR = 129/7567, NEX = 1.5, field of view (FOV) = 220 × 220 mm, acquisition matrix 448 × 256 256
Table 1 Example for an MR imaging protocol of the knee Orientation Sequence type Repetition time / echo time [ms] Fat suppressed Resolution (mm) Acquisition time [ms] sagittal proton-densitiy turbo spin echo 3000 / 29 No 0.2.
For primary tumour detection and delineation, an echo-planar diffusion-weighted imaging (DWI) sequence was used in a transverse plane with following parameters: 4 mm slice thickness, voxel size 3.0 × 3.0 × 4.0 mm, acquisition time approximately 5 min. Six b values were applied (b = 0, 50, 100, 500, 750 and 1,000 s/mm2) to calculate the apparent diffusion coefficient (ADC).
The 3D model of the porcine tibial bone was created by scanning the bone (without containing the implant) on a low-field MRI (0.25 T) (Esaote G-scan brio) with a 3D SHARC sequence (TR/TE 25/12.5, slice thickness 0.4 mm, acquisition time 5 38, field of view 200 mm with a matrix of 512 × 512).
A T1-weighted high-resolution three-dimensional anatomical volume was also acquired, by using a 3D-modified driven equilibrium Fourier transform (MDEFT) sequence (field of view: 256 × 224 × 176 mm; resolution: 1.333 × 1.750 × 1.375 mm; acquisition matrix: 192 × 128 × 128 pixels; reconstruction matrix: 256 × 128 × 128 pixels).
Similarly as described in ISO guideline for RSA studies. ISO 16087 2013) During each of the 12 acquisitions, the phantom was scanned in a transverse direction on a low-field MRI with a 2D PD-weighted metal artifact reduction sequence (MARS) PD-XMAR (TR/TE 1020/10, slice thickness 3 mm, acquisition time 5 08 min, field of view 180 mm with a matrix of 224 × 224).
T2-weighted fast recovery fast spin echo MRI was performed in the axial, sagittal, and coronal planes, respectively, with the following parameters: TR/TE 3000/102 108; field of view 26 28 cm; slice thickness 4 mm interleaved; gap 1 mm; acquisitions 2. Scan time was less than 10 min, and 90 continuous images were obtained.
However, for patients undergoing a targeted CT solely for the assessment of body composition, a limited low-dose axial 10-mm acquisition at the L3 level may be appropriate: 120 kV, <80 mAs, soft tissue reconstruction algorithm, matrix of 512 × 512 and FOV of 30-35 cm with the advantage that the additional radiation exposure from a limited CT is small and is equivalent to a chest radiograph [56].
Such a signal reduction -which also occurs but to a lesser extent for US imaging - would have resulted in US imaging slightly outperforming PA imaging (i.e., with theoretical contrasts of 24.3 dB and 22.9 dB, respectively) for the 13-mm acquisition had the seed been imaged in the short-axis orientation.
For the 4-mm acquisition, theoretical contrast calculations suggest that PA imaging would have still outperformed US imaging had the seed been imaged in the short-axis orientation, with a slightly reduced contrast improvement (i.e., PA imaging over US imaging) of 24.4 dB (compared to a 27.9-dB improvement) being realized in this case.
