Evaluation of the single scatter simulation algorithm implemented in the STIR library

The model-based single scatter simulation (SSS) algorithm has been implemented in the Open Source software library called STIR (Software for Tomographic Image Reconstruction). The main advantage of the SSS algorithm is its good accuracy at small computational time. The aim of the current work is to validate our implementation and to investigate the influence of several parameters. The validation tests are based on the NEMA-NU 2001 standard about scatter accuracy. The results of our implementation are compared both with data from the SimSET Monte Carlo simulation package and with measured data. The flexibility of our code can help us to understand the influence of many parameters of the algorithm, such that optimal values can be found for given time constraints, as for example are the detector sampling and the voxel size of the transmission image. This implementation will be included in future distributions of STIR.