Advanced Physics for Brachytherapy 2018

How efficient can MC be …?

t

scales with N, type A uncertainty scales with

CALC

➢ The only means to decrease t

for a given level of type A uncertainty is

CALC

variance reduction.

➢ Variance reduction: • Simple techniques: geom. truncation, E cut off, phase space files*, analytical primary scatter separation (PSS), …

(* Pantelis et al. On source models for 192Ir HDR brachytherapy dosimetry using model based algorithms Phys. Med. Biol. 61, 2016)

• Elaborate techniques**: techniques to bias the sampling distributions while using correction factors to eliminate the biasing effect in the sample mean of the quantity of interest (** see Sheikh-Bagheri, D., Kawrakow, I., Walters, B., and Rogers, D.W.O. 2006. Monte Carlo simulations: Efficiency improvement techniques and statistical considerations. Integrated New Technologies into the Clinic: Monte Carlo and Image-Guided Radiation Therapy—Proceedings of the 2006 AAPM Summer School)