SS3D-fast fully 3-D PET iterative reconstruction using stochastic sampling

We have developed a three dimensional (3D) reconstruction procedure for Positron Emission Tomography using stochastic sampling techniques-the SS3D algorithm. A forward and back-projector pair has been developed which eliminates the need to explicitly calculate the system response matrix (SRM). This is advantageous as it eliminates the memory requirements for storing this matrix. As compared to on-the-fly methods, our method is more accurate in its assumptions and can readily incorporate various physical effects of attenuation, scatter and detector characteristics. This method can be efficiently used with “simultaneous” or “row action” algorithms like ISRA, EM and OSEM. We demonstrate the successful implementation of this technique with the ML-EM, MAP-EM, and MAP-OS-EM algorithms by evaluating the images on the basis of uniformity of noise, contrast recovery, signal to noise ratio, point spread function, structural accuracy and computational time