Extension of axial coverage and artifact reduction in iterative reconstruction in computed tomography

It is well known that iterative reconstruction (IR) of a long object is a challenge in case of circular trajectory. Axial artifacts occur naturally in IR due to data truncation. Because IR uses reprojection, axial coverage of the reconstruction field of view reduces with each iteration. In this work we present a method to extend axial coverage and reduce artifacts in the circular cone-beam scanning geometry. Our approach is based on our recently presented weighted iterative reconstruction algorithm. We use extended FDK reconstruction for FBP seed, expansion of detector rows in Z direction, and a special axial weight designed to reduce artifacts caused by data truncation. Evaluation shows that sharp streaks at the edge of the reconstruction volume are removed and good image quality in the extended region is achieved.