Iterative Reconstruction of {SPECT} Images using Adaptive Multi-Level Refinement
H. Schumacher and S. Heldmann and E. Haber and B. Fischer
    318 -- 323  (2008)

We present a novel method for iterative reconstruction of high resolution images. Our method is based on the observation that constant regions in an image can be represented at much lower resolution than region with fine details. Therefore, we combine adaptive refinement based on quadtrees with iterative reconstruction to reduce the computational costs. In our experiments we found a speed up factor of approximately two compared to a standard multi-level method