Line segments are classified according to orientation to improve list mode reconstruction of tomography data using graphics processing units (GPUs). The new approach addresses challenges which include compute thread divergence and random memory access by exploiting GPU capabilities such as shared memory and atomic operations. The benefits of the GPU implementation are compared with a reference CPU-based code. When applied to positron emission tomography (PET) image reconstruction, the GPU implementation is 43× faster, and images are virtually identical. In particular, the deviation between the GPU and the CPU implementation is less than 0.08% (RMS) after five iterations of the reconstruction algorithm, which is of negligible consequence in typical clinical applications.
Shift-varying line projection using graphics hardware