Application of nonrigid registration in liver cancer treatment

A semiautomatic nonrigid registration is proposed to match preoperative CT images and real-time MR images during the ablation of liver tumors. The method includes three parts. Firstly, the livers are extracted from CT and MR images. Since the CT image is acquired a several days before surgery, there is enough time for surgeons to segment the liver from the CT image manually. During the surgery, active contour is used to extract the liver from the MR image. Then, affine registration to match the images roughly. Finally, high accuracy registration is reached by free-form deformation registration. The results are evaluated by visual inspection and the distance of two liver surfaces. The error of liver surfaces is within 1.5 mm and the result of visual inspection is very well.