The routine to add scatter to the simulation is defined by

cfg.callback_scatter = 'Scatter_ConvolutionModel';

If cfg.callback_scatter is empty ([]), no scatter will be simulated. ScatterConvolutionModel uses a simple sinogram-based scatter estimation and requires the following parameters :

cfg.scatter_level = 0.001;
cfg.scatter_smoothing = 10;

cfg.scatter_level is the scatter fraction relative to the airscan, i.e., scatter-to-air ratio (SAR), NOT scatter-to-primary ratio (SPR). Using 0.0 will eliminate scatter.

SAR should be on the order of 0.001 or so. The reason it was not defined by SPR is that it was not completely obvious how to define the primary level.

cfg.grid_height specifies the height of anti-scatter grid. This is only used for Monte Carlo reconstruction.

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