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. Differences between TOF dependent and non-TOF dependent scatter are characterized. Because TOF scoring removes the degeneracy in ray sum calculations, TOF SSS requires about 16 times longer to compute the scatter estimate than non-TOF SSS. However, when overhead such as image computation and iteration is factored in, the clinical performance is only a factor of five slower