Three-dimensional nonrigid registration and fusion for image-guided surgery navigation system

High Intensity Focused Ultrasound (HIFU) system has been successfully applied to the tumor therapy. It is crucial to localize the tumor region accurately in this system. In this paper, a semi-automatic non-rigid registration algorithm is presented to implement the image-guided surgery navigation and localization by registration of pre-operative CT/MRI images and intra-operative US images. The global motion of object is modeled by an affine transformation while the local deformation is described by Free-Form Deformation (FFD) based on B-splines. By experiments on simulated and real data, the registration results show that new registration algorithm is appropriate for clinical applications, and can satisfy the requirements of localization system of HIFU. It also indicates that image-guided surgery navigation technique has potential use in HIFU therapy system using our registration algorithm.