OMPI Seminar: Stephen Deering and Ernesto Mainegra-Hing

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Thursday, January 19, 2017

Time: 3:30 - 5:00 pm - Thursday 19 January 2017. Refreshments start at 3:15 pm.

Location: East Foustenallas Auditorium (H2368), Second Floor, The University of Ottawa Heart Institute, 40 Ruskin Street.

1) Calculating Dose Distributions with EGS Brachy - A new EGSnrc user code

By Stephen Deering, MSc student, Carleton University, Supervisor: Dr. Rowan Thomson

Abstract: egs_brachy is a new, efficient Monte Carlo user code which has been developed in order to enable more accurate brachytherapy dose calculations for both research and clinical applications. This talk will present some preliminary research done using egs_brachy, in the form of dose calculations for ocular and breast brachytherapy. For ocular brachytherapy, depth dose curves were calculated and benchmarked for a large range of photon and beta-emitting eye plaques, which are widely used in the treatment of intraocular tumors. Then, the ability of egs_brachy to provide a comprehensive look at model-based dose calculations for permanent seed implant breast brachytherapy will be discussed. These two topics show a small sample of the possible uses for egs_brachy and provide good examples to introduce both the user code and its ability to improve on current model-based dose calculations.

2) Accuracy of electron transport in the presence of magnetic fields with EGSnrc

By Ernesto Mainegra-Hing, PhD, National Research Council Canada

Abstract: Since the 2016 release, EGSnrc, a well-known toolkit for the Monte Carlo simulation of electron, positron and photon transport, allows the inclusion of the effect of electromagnetic fields on the transport of charged particles. EGSnrcā€™s main strength resides in its ability to transport charged particles accurately and efficiently thanks to its charged particle transport algorithm and exact multiple scattering theory. The approach used to model the transport of charged particles in the presence of a magnetic field is described, and its accuracy tested by means of a modified Fano test, valid under very specific conditions. Fano tests are carried out for an ion chamber and a slab geometry of varying density showing that accurate results can only be obtained when restricting charged particles to take very small condensed-history steps. The impact on simulation time is discussed as well as the possibility of increasing calculation efficiency using variance reduction techniques.