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SU‐FF‐T‐626: Dynamic Splitting of Gaussian Pencil Beams in Heterogeneity‐Correction Algorithms for Radiotherapy with Heavy Charged Particles
Author(s) -
Kanematsu N,
Komori M,
Yonai S,
Ishizaki A
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3182124
Subject(s) - pencil beam scanning , pencil (optics) , proton , proton therapy , gaussian , imaging phantom , beam (structure) , dosimetry , bragg peak , physics , computational physics , range (aeronautics) , ion , scattering , optics , atomic physics , materials science , nuclear physics , nuclear medicine , quantum mechanics , medicine , composite material
Purpose: To develop an algorithm to resolve intrinsic problems with dose calculations using pencil beams when particles involved in each beam are overreaching a lateral density interface or when they are detouring in a laterally heterogeneous medium. Method and Materials: A finding on a Gaussian distribution, such that it can be approximately decomposed into multiple narrower, shifted, and scaled ones, was applied to dynamic splitting of pencil beams implemented in a dose calculation algorithm for proton and ion beams. The method was tested in an experiment with a range‐compensated carbon‐ion beam. Its effectiveness and efficiency were evaluated for carbon‐ion and proton beams in a heterogeneous phantom model. Results: The splitting dose calculation reproduced the detour effect observed in the experiment, which amounted to about 10% at a maximum or as large as the lateral particle‐disequilibrium effect. The proton‐beam dose generally showed large scattering effects including the overreach and detour effects. The overall computational times were 9 s and 45 s for non‐splitting and splitting carbon‐ion beams and 15 s and 66 s for non‐splitting and splitting proton beams. Conclusions: The beam‐splitting method was developed and verified to resolve the intrinsic size limitation of the Gaussian pencil‐beam model in dose calculation algorithms. The computational speed slowed down by factor of 5, which would be tolerable for dose accuracy improvement at a maximum of 10%, in our test case.