Determination of the relative orientation of projections of asymmetric objects

The ability to determine the relative view orientation of objects from their projections has enabled well established tomographic techniques to be employed in the three-dimensional reconstruction of objects from images obtained via modalities where the orientation of the objects cannot be controlled. Most techniques used to determine particle orientation from projections assume that the particle exhibits some form of symmetry. A method is described for the determination of the relative view orientation of randomly acquired projections of asymmetric objects. It extends upon the projection slice theorem by determining the relative orientation of projections by the location of lines of intersection among the Fourier transforms of the projections in three-dimensional Fourier space. The complete algorithm is described and its efficacy is demonstrated using real data