High-quality parallel-ray X-ray CT back projection using optimized interpolation
Mike McCann, EPFL STI LIB

Meeting • 11 October 2016 • BM 4 233

Abstract
Our X-ray reconstruction scheme relies on back projection of the measurements into the reconstruction domain, but computing this exactly is slow. In our previous work, we accelerated this with interpolation: we fit a continuous representation to samples of the signal, then sampled it at the required locations. In this work, we use a spline interpolation trick to improve the accuracy of the interpolation. Specifically, we apply a prefilter that orthogonally projects the underlying signal onto the space spanned by the interpolator before sampling it. We then build on this idea by using oblique projection, which simplifies the computation while giving effectively the same improvement in quality. Our experiments on analytical phantoms show that this refinement can improve the reconstruction quality for both filtered back projection and iterative reconstruction.