Real-time registration of 3D cerebral vessels to x-ray angiograms

Abstract

A quick method to obtain the 3D transformation of a 3D freeform shape model from its 2D projection data is proposed. This method has been developed for the real-time registration of a 3D model of a cerebral vessel tree, obtained from pre-operative data (eg. MR Angiogram), to a X-ray image of the vessel (eg. Digital Subtraction Angiogram) taken during an operation. First, the skeleton of the vessel in a 2D image is automatically extracted in a model-based way using a 2D projection of a 3D model skeleton at the initial state (up to ±20 degree difference in rotation). Corresponding pairs of points on the 3D skeleton and points on the 2D skeleton are determined based on the 2D Euclidean distance between the projection of the model skeleton and the observed skeleton. In the process, an adaptive search region for each model point, which is determined according to the projected shape, effectively removes incorrect correspondences. Based on a good ratio of correct pairs, linearization of a rotation matrix can be used to rapidly calculate the 3D transformation of the model which produces the 2D observed projection. Experiments using real data show the practical usefulness of the method.