SPECT reconstruction on the GPU

With the increasing reliance of doctors on imaging procedures, not only visualization needs to he optimized, but the reconstruction of the volumes from the scanner output is another bottleneck. Accelerating the computationally intensive reconstruction process improves the medical work flow, matches the reconstruction speed to the acquisition speed, and allows fast batch processing and interactive or near-interactive parameter tuning. Recently, much effort has besen focused on using the computational power of graphics processing units (GPUs) for general purpose computations. This paper presents a CPU-accelerated implementation of single photon emission computed tomography (SPECT) reconstruction based on an ordered-subset expectation maximization algorithm. The algorithm uses models for the point-spread-function (PSF) to improve spatial resolution in the reconstruction imasses, Instead of computing the PSF directly, it is modeled as efficient blurring of slabs on the GPU in order to accelerate the process, The algorithm for the calculation of accumulated attenuation factors that allows correcting the generated volume according to the attenuation properties of the volume is optimised for processing on the GPU, Since these factors can be reused between different iterations, a cache is used that is adapted to different sizes of the video memory so that only those factors have to be recomputed that do not fit onto graphics memory, These improvements make the reconstruction of typical SPECT volume near interactive.