MR-CT image registration in liver cancer treatment with an open configuration MR scanner

MR - CT image registration has been used in the liver cancer treatment with an open MR Scanner to guide percutaneous puncture for ablation of tumors. Due to low magnetic field and limited acquisition time, MR images do not always show the target clearly. Sometimes, assistance of CT images is helpful for the navigation to the target. The shape of the liver within the surgical procedure is different from that of preoperative CT images due to the patient position for the convenience of surgery. It is quite difficult to match the images accuracy during surgery. In this paper, we have proposed a method to improve the registration accuracy of images with an open MR scanner and preoperative CT images of the liver. The method includes three parts. Firstly a semiautomatic method is used to extract the liver from MR and CT images as region of interest (ROI). Then, an affine registration is used to match the images roughly. Finally, BSpline-based nonrigid registration is applied. The results are found to be satisfactory with visual inspection by experts and with evaluation by the distance of two liver surfaces, while comparing with other methods.