Registration of CT and MRI volume data of the liver

The paper introduces a way to improve treatment planning of single-dose radiation therapy of liver tumors. Therefore, a new algorithm for the registration of diagnostic magnetic resonance images (MRI) and the computed tomography (CT) data used for treatment planning was developed. The described algorithm is divided into two stages. First, the two data sets are aligned by optimization of mutual information using rigid transformations. After this initial registration step, a nonrigid transformation based on thin-plate splines is performed, modeling the deformations of the soft tissue. An algorithm for automatic control point computation was developed, which is supposed to simplify the time-consuming task of defining the control points necessary for a thin-plate spline interpolation. The obtained results show that the implemented algorithm can successfully solve the registration problem.