Automated recovery of the center of rotation in optical projection tomography in the presence of scattering

Finding the center of rotation is an essential step for accurate 3-D reconstruction in optical projection tomography. Unfortunately, current methods are not convenient since they require either prior scanning of a reference phantom, small structures of high intensity existing in the specimen, or active participation during the centering procedure. To solve these problems this paper proposes a fast and automatic center of rotation search method making use of parallel programming in graphics processing units. Our method is based on a two step search approach making use only of those sections of the image with high signal-to-noise ratio. We have tested this method both in nonscattering ex vivo samples and in in vivo specimens with a considerable contribution of scattering such as Drosophila melanogaster pupae, recovering in all cases the center of rotation with a precision 1/4 pixel or less.