Image registration is a valuable technique for medical diagnosis and treatment. In this paper, we present an enhanced implementation of the popular iterative closest point (ICP) algorithm developed for the registration of 3D free-form closed surfaces. The main step of the ICP consists of finding the closest points between data sets which are then used to estimate the parameters of the global rigid transformation. We propose a new technique based on the use of a look up matrix for finding the best correspondence pairs. The algorithm, called Comprehensive ICP (CICP) algorithm, is then successfully applied for the registration of 3D data of the left ventricle of the heart, acquired using two different medical imaging modalities.