Several Practical Problems in Clinical Head CT Image Registration

This paper is about some practical problems related to image registration of clinical head CT images. The process of image registration is to bring two or more images into spatial alignment. The first step in image registration is to know correct image orientation relative to the world coordinates. The clinical head computed tomography (CT) images have several special features. One is related to different scanning protocol. Usually for detail information on posterior fossa, doctors do two series scan which have thinner slice thickness on the bottom part of the whole brain than the top part to result in two different slice spacing in the two series volumes. The second feature is related to CT gantry tilt angle. In clinical practice, physicians are required to tilt the CT gantry to prevent the X-ray exposure to eyes and other sensitive organs. The resultant image volume has geometrical distortion need to correct. The third feature is about patient position and patient orientation. All of these features need to be reconsidered in the clinical registration applications. We must check the correct image header carefully to get the detail information from head CT images for better registration results.