Automatic registration of whole body serial micro CT images with a combination of point-based and intensity-based registration techniques

Registration of image volumes acquired over time is important for tasks that include measurements and quantification of temporal changes such as variations in tumor size, shape, or characteristics in response to therapy. A number of methods have been proposed over the years to address this problem but whole body registration of small animals presents special challenges because these images contain many articulated joints and because the animals cannot be easily placed in the same position from acquisition to acquisition. This paper presents a new method for the automatic registration of whole body CT volumes, which consists of two steps. Skeletons are first brought in approximate correspondence with a point-based method. Transformations so obtained are refined with an intensity-based algorithm. The approach has been tested on serial image volumes of a mouse acquired with a micro CT. We demonstrate that the approach we propose can successfully register image volumes even when the limbs are in very different positions as is often the case for small animals