Analytic reconstruction for helical-orbit cone-beam SPECT

Helical-orbit cone-beam (CB) single-photon emission computed tomography (SPECT) provides improved sensitivity and also acquires a complete data set for the reconstruction of a three-dimensional (3D) source distribution. The authors have developed an analytic helical-orbit CB SPECT reconstruction algorithm that can be decomposed into three steps. The algorithm first rebins helical-orbit CB SPECT data into plane-integral space, then multiplies the rebinned data with normalization factors that compensate for the non-uniform sampling of CB SPECT systems, and finally uses a direct Fourier inversion method for the 3D reconstruction from the normalized plane integrals. The authors have also developed a method to speed up the rebinning procedure. After testing the algorithm with simulated mathematical Defrise phantoms, the authors found that helical-orbit CB SPECT produces fewer image artifacts than does a circular-orbit CB SPECT, and they also found that using a triple-camera helical-orbit CB SPECT system, which results in more uniform sampling, can further suppress the artifacts