Cone-beam Tomography from Short-Scan Circle-plus-Arc Data Measured on a C-arm System

In C-arm computed tomography (CT) systems, the source trajectory does not follow an ideal trajectory. Thus, the real data acquisition geometry is typically expressed by a sequence of projection matrices. However, exact reconstruction algorithms are based on an analytic expression of the projection geometry. In this work, we present a reformulation of an exact reconstruction method to handle projection matrices. In particular, the M-line approach is investigated for a short-scan circle-plus-arc data acquisition. The computation of the derivative with respect to the source trajectory is numerically most critical for which a novel and stable implementation is developed. In order to determine the backprojection range, a 2D polygonal weighting scheme is proposed. Image results are presented from phantom data acquired by a Siemens AXIOM Artis C-arm system. Excellent image results are achieved. Due to the complete data acquisition, the problem of cone artifacts is totally resolved.