Reprojection using a parallel backprojector.

Reprojection is the process by which projections are produced from an image, such that if these projections are filtered and backprojected, they yield the original image. In computed tomography, applications of reprojection include its use in algorithms for iterative beam hardening correction, metal artifact removal, and streak suppression. However, because of the computational expense of reprojection, algorithms that employ this process have never been widely used. A method will be presented that enables an unmodified backprojector to be used as a reprojector. Because backprojectors are designed to exploit the parallelism in the backprojection algorithm, the time required to obtain reprojections is significantly reduced.