Region-of-interest imaging with differentiated backprojection and angularly subsampled complementary sinograms

International audience<p>Recently, we introduced a two-pass analytical recon-struction that allows truncation to be accounted for in the imagedomain rather than the projection domain. In particular, weshowed that backprojection of a vastly angularly undersampledsinogram of un-truncated data could be used to extrapolate thebackprojection of a finely sampled, fully truncated sinogramof the same object to perform more accurate region-of-interest(ROI) imaging. The same extrapolation idea can be performedusing differentiated backprojection (DBP). The goal of this studyis to give a general DBP-based formula when reconstructinga finite set of projections in parallel geometry. We discuss thediscretization of this formula, in particular when the image gridsize is large with respect to the number of projections, and weshow how it can be applied to our extrapolation problem.