  In application of tomography imaging, limited-angle problem is a quite
practical and important issue. In this paper, an iterative
reprojection-reconstruction (IRR) algorithm using a modified Papoulis-Gerchberg
(PG) iterative scheme is developed for reconstruction from limited-angle
projections which contain noise. The proposed algorithm has two iterative
update processes, one is the extrapolation of unknown data, and the other is
the modification of the known noisy observation data. And the algorithm
introduces scaling factors to control the two processes, respectively. The
convergence of the algorithm is guaranteed, and the method of choosing the
scaling factors is given with energy constraints. The simulation result
demonstrates our conclusions and indicates that the algorithm proposed in this
paper can obviously improve the reconstruction quality.
