Grey value correlation techniques used for automatic matching of CT and MR brain and spine images

Grey value correlation is generally considered not to be applicable to matching of images of different modalities. In this paper we will demonstrate that, with a simple preprocessing step for the Computed Tomography (CT) images, grey value correlation can be used for matching of Magnetic Resonance Imaging (MRI) with CT images. Two simple schemes are presented for automated 3D matching of MRI and CT neuroradiological images. Both schemes involve grey value correlation of the images in order to determine the matching transformation. In both schemes the preprocessing consists of a simple intensity mapping of the original CT image only. It will be shown that the results are insensitive to considerable changes in the parameters that determine the intensity mapping. Whichever preprocessing step is chosen, the correlation method is robust and accurate. Results, compared with a skin marker-based matching technique, are shown for brain images. Additionally, results are shown for an entirely new application: matching of the cervical spine.