Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET

We extend the single scatter simulation (SSS) algorithm for scatter correction of three dimensional positron emission tomography to include the case in which the scattered annihilation radiation is discriminated according to its differential time-of-flight (TOF). Good agreement between computed and measured TOF dependent scatter is observed in phantom and human data. Significant differences between TOF dependent and non-TOF dependent scatter are found. Because TOF scoring removes the degeneracy in ray sum calculations, TOF SSS takes about seven times longer than non-TOF SSS to compute the scatter sinogram itself. However, when the overhead due to image computation and iteration is factored in, the clinical performance is only a factor of three slower.