A comparative study of angular extrapolation in sinogram and stackgram domains for limited angle tomography

Abstract

In limited angle tomography, the projection views over a complete angular range of 180° are not available for image reconstruction. The missing part of the projection or sinogram data need to be extrapolated numerically, if standard image reconstruction methods are applied. A novel stackgram domain can be regarded as an intermediate form of the sinogram and image domains, in which the signals along the sinusoidal trajectories of a sinogram can be processed independently. In this paper, we compare extrapolation of incomplete sinogram data in the sinogram and stackgram domains along the angular directions. The extrapolated signals are assumed to be band-limited, other a priori assumptions about the data are not made. In this study, we employed simulated numerical data with different ranges of the limited projection views. According to our experiments, extrapolation of the incomplete data in the stackgram domain provides quantitatively better results as compared to extrapolation in the sinogram domain. In addition, tangential degradation in the reconstructed images can not be observed in the case of stackgram extrapolation, in contrast to angular sinogram extrapolation. © Springer-Verlag Berlin Heidelberg 2005.