Assessment of Hepatocellular Carcinoma Ablation Margins Using Fused Pre-ablation Hepatobiliary Phase and Post-ablation Unenhanced T1-weighted Images

This study retrospectively investigated the value of fusing a pre-ablation hepatobiliary phase（HBP）series and post-ablation unenhanced T1-weighted images（T1WIs）to evaluate the treatment effectiveness of radiofrequency ablation for hepatocellular carcinoma（HCC）. Predictors of local tumor progression（LTP）were also identified. Our study comprised 47 patients with 88 HCCs（＞2 years follow up）who underwent pre-ablation gadoxetate disodium-enhanced magnetic resonance imaging and post-ablation T1-weighted imaging. For the new assessment, pre-ablation HBP series and post-ablation T1WIs were fused using a rigid registration and manual correlation, and the ablation margin appearance was classified as ablation margin（＋）, ablation margin zero, ablation margin（−）, or indeterminate（index tumor was invisible）based on the post-ablation T1WIs and fusion images. The minimal ablation margin was measured and clinical factors were investigated to identify other risk factors for LTP, which was observed in 14 tumors. The mean minimal ablation margin was 1.9mm, excluding 5 indeterminate nodules without LTP, and 8 ablation margin-zero HCCs with LTP, with multivariate logistic regression analysis showing that the likelihood of ablation margin＋was inversely proportional to tumor size. The independent risk factors for LTP were not identified, but the cumulative LTP rates（0％ at 1, 2, and 3 years）in 41 ablation margin＋ nodules were significantly lower（P＝0.005）than those（8.8％, 17.6％, and 17.6％ at 1, 2, and 3 years, respectively）in 34 ablation margin-zero nodules. In conclusion, fusion images might show an early therapeutic response of the ablated tumors in the majority of HCC cases