Synthetic scanner arrays in tomographic reconstructionsfrom fan- and cone-beam projections

A deterministic method for artifact-free reconstruction from truncated sets of fan-beam projections thatextends the artifact-free zone of fan-beam scanners is presented. Truncated partial sets of projectionsare merged into a complete virtual set of projections before reconstruction through synthetic scannerarrays. The reconstruction from the virtual set of projections yields the artifact-free representation ofthe whole object needed for evaluation of its global structure. The extent of the artifact-free zone in reconstructions from cone-beam projections is evaluated. The concept of synthetic linear and circular scanner arrays for reconstruction from truncated sets of projections is extended to cone-beam geometry. It is shown that linear scanner arrays are not directly applicable to cone-beam geometry but yieldreasonable approximations if the partial sets of projections are resorted into a virtual set of wedge-beam projections before reconstruction. The presented solution constitutes a practical and exact det rministic method of horizontally extending the artifact-free zone in cone-beam geometry. The extension of the vertical limits of the artifact-free zone is discussed. The proposed methods provide a practical low-cost approach to artifact-free reconstruction of large objects. Illustrative examples are provided.