Application of non-rigid medical image registration on open-MR based liver cancer surgery

A semi-automatic non-rigid registration technique is applied to assist and improve the open magnetic resonance (Open-MR) imaging guided liver cancer surgery in which cancer tissues are coagulated by microwave ablation. Since the Open-MR volumes are obtained in a lower magnetic field (0.5 T), their qualities are not always sufficient to visualize tumors clearly. Combination of CT volumes acquired before surgery will be helpful to show the tumor's location by application of registration techniques. Since such a registration problem belongs to a non-rigid one considering the easy deformation of livers, free-form deformation based registration method is applied, cooperated with mutual information and multi-resolution strategy. Registration accuracy is evaluated by calculating the distance of tumor's boundaries on Open-MR and registered CT images. Experiments show that the registration is accurate enough (≈ 1.5 mm) for liver cancer surgery given some proper processing steps.