2.2. Imaging

MRI was performed on a 3.0T MR scanner (Ingenuity, Philips Healthcare, Best, The Netherlands) utilizing a 16-channel H&N coil. DWI was performed by fat-suppressed single shot spin-echo echo-planar imaging; TR = 500 ms; TE = 105 ms; echo-planar imaging factor = 35; field of view = 230 × 230 mm; slice thickness = 2 mm; intersection gap = 0.3 mm; matrix = 128 × 128 and receiver bandwidth = 2735.7 Hz per pixel. A total of 10 b-values were used: 0/10/25/50/75/150/300/500/750/1000 s/mm². The ADC map was produced by vendor-provided software.

DCE-MRI was performed by 3 dimensional T1-weighted fat-field echo (FFE); TR/TE = 4.8/2.4 ms; flip angle = 12; FOV = 230 × 230 × 180 mm; matrix = 144 × 144; 75 dynamic acquisitions of 4.16 s and signal averages = 2. An intravenous bolus injection of 0.2 mL/kg of body weight Gd-DOTA (Dotarem, Guerbet, Villepinte, France) was administered after 3 dynamic acquisitions (3 mL/s followed by 25 mL saline flush). The dynamic scan was preceded by 5 scans with the same parameters as the DCE-MRI scan with varying flip angles (2°/5°/10°/15°/20°). This was performed to estimate the quantitative native T1 maps, which were used to convert the signal intensity of the DCE scan into a contrast agent concentration curve, which was used for calculating DCE-derived parametric maps [14].

¹⁸F-FDG-PET/low-dose CT was performed according to EANM guidelines 2.0 on an EARL accredited Gemini TF-PET/CT (Philips Healthcare, Best, The Netherlands) [15]. The low-dose CT parameters were 120 kV and 30 mAs. Whole body ¹⁸F-FDG-PET/CT was performed in an arms down position, from the mid-thigh-to-skull vertex, 60 min after intravenous administration of 2.5 MBq/kg ¹⁸F-FDG, 2 min/bed position. ¹⁸F-FDG-PET images were reconstructed by vendor-provided reconstruction protocol, with photon attenuation correction, matrix size = 144 × 144 and voxel size = 4 × 4 × 4 mm. Post-reconstruction resolution was 6.75 mm, full width at half maximum.