Magnetic Resonance Imaging Findings After Percutaneous Irreversible Electroporation of Liver Metastases

OBJECTIVE The aim of this study was to systematically investigate the course of magnetic resonance (MR) signal intensity (SI) changes that occur in noncirrhotic livers after irreversible electroporation (IRE) of liver metastases. METHODS This study is an institutional review board-approved prospective longitudinal follow-up study on 27 patients with 37 liver metastases who underwent computed tomography-guided percutaneous IRE and a standardized follow-up protocol by serial hepatic MR imaging studies that consisted of a gadobutrol-enhanced dynamic series, axial T2-weighted (T2w) turbo spin echo, and diffusion-weighted imaging (b = 0/50/800), acquired before, within 2, and at 24 hours after IRE; at 1, 2, 4, 6, 8, and 12 weeks after IRE; and every 3 months thereafter for a follow-up of at least 12 months. RESULTS The ablated target lesion remained visible within the ablation zone in 23 (62%) of 37 of cases for a mean time of 21 ± 20 weeks (median, 12 weeks). The ablation zone appeared homogeneously hyperintense on T2w turbo spin echo images on the day of IRE in 37 of 37 cases. By 24 hours after IRE, the ablation zone inverted its SI in 35 of 37 cases to intermediately hypointense, with a rim of T2w bright SI that exhibited arterial phase enhancement; this persisted for 7 ± 5 weeks (median, 4 weeks). The rim resolved in 35 (95%) of 37 cases within 3 months. The ablation zone increased slightly over the first 48 hours, then shrank progressively. Complete healing of the ablation zone was observed in 57% (21/37) after an average of 14 ± 15 (median, 8 weeks).Average apparent diffusion coefficient values of the ablation zone decreased from 0.74 ± 0.36 × 10 mm/s pre-IRE to 0.63 ± 0.27 × 10 mm/s within the first 24 hours (P < 0.05), followed by a progressive normalization to 0.91 ± 0.30 × 10 mm/s at 2 months. CONCLUSIONS Knowledge of the broad spectrum of MR imaging findings after IRE is important to avoid diagnostic errors in the follow-up of patients after IRE.