Image recovery in computer tomography from partial fan-beam data by convex projections

For the image recovery process the authors use the convex projections method, also known as the method of projections onto convex sets (POCS). Several incomplete-data geometries, including those associated with limited source travel and beam-blocking internal opacities, are considered. To enable the recovery several prior-knowledge constraints including one associated with the directivity of the image vector are used. The overall recovery algorithm can be practically implemented by exploiting the Toeplitz structure of key operators