MRI examination

All patients were scanned in a supine position on a 1.5T (Magnetom Avanto, SIMENS) or a 3.0T whole-body MRI scanner (Discovery MR750, GE Healthcare) with an eight-channel phased-array torso coil centered over the abdomen. The routine contrast-enhanced liver MRI protocol included in-phase and out-of-phase, T2-weighted, diffusion-weighted (DW), unenhanced T1-weighted, dynamic, transitional-phase (TP) and hepatobiliary-phase (HBP) sequences. For dynamic phase imaging, the contrast agent gadopenate meglumine (Magnevist; Bayer Healthcare) or gadoxetic acid (Primovist; Bayer Healthcare) was injected through the elbow vein or the dorsal hand vein at a dose of 0.2 mL/kg or 0.025 mmol/kg body weight at a rate of 1–2 mL/s, followed by a 20-mL saline flush. Double-phase arterial phase (AP) images were obtained 18 s (early AP) and 28 s (late AP) after the contrast agent arrived at the thoracic artery using bolus triggering. Portal venous-phase (PVP) and delayed phase (DP) images were obtained 60 s and 4 min for gadopenate meglumine enhancement, while TP and HBP images were obtained 3 min and 15–20 min after gadoxetic acid administration, respectively. The scanning parameters are listed in Table E1.