MRI non-rigid registration with tumor contraction correction for ablative margin assessment after microwave ablation of hepatocellular carcinomas

Abstract

Objective: This study aims to develop and assess a tumor contraction model, enhancing the precision of ablative margin(AM) evaluation after microwave ablation (MWA) treatment for hepatocellular carcinomas (HCCs). 
Approach: We utilize a probabilistic method called the Coherent Point Drift algorithm to align pre-and post-ablation MRI images. Subsequently, a nonlinear regression method quantifies local tumor contraction induced by MWA, utilizing data from 47 HCC with viable ablated tumors in post-ablation MRI. After automatic non-rigid registration, correction for tumor contraction involves contracting the 3D contour of the warped tumor towards its center in all orientations.
Main Results: We evaluate the performance of our proposed method on 30 HCC patients who underwent MWA. The Dice similarity coefficient between the post-ablation liver and the warped pre-ablation livers is found to be 0.95±0.01, with a mean corresponding distance between the corresponding landmarks measured at 3.25±0.62mm. Additionally, we conduct a comparative analysis of clinical outcomes assessed through MRI over a 3-month follow-up period, noting that the AM, as evaluated by our proposed method, accurately detects residual tumor after MWA.
Significance: Our proposed method showcases a high level of accuracy in MRI liver registration and AM assessment following ablation treatment. It introduces a potentially approach for predicting incomplete ablations and gauging treatment success.