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SU‐E‐T‐683: Improvement of LDR Brachytherapy TG‐43 Dose Calculations with a GPU‐Accelerated Raytracing Algorithm
Author(s) -
Bourque A,
Gariépy J,
Mathieu D,
Hissoiny S,
Beaulieu L,
Després P
Publication year - 2011
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 - 10.1118/1.3612645
Subject(s) - brachytherapy , monte carlo method , formalism (music) , imaging phantom , algorithm , voxel , dosimetry , computer science , computational physics , physics , nuclear medicine , materials science , mathematics , optics , radiation therapy , statistics , artificial intelligence , medicine , art , visual arts , musical
Purpose: To compare a fast GPU‐based dose calculation algorithm to Monte Carlo (MC) simulations and TG‐43 results in low dose rate brachytherapy, in terms of accuracy and relative execution speed. Methods: Dose calculations were performed in a voxelized numerical phantom comprising bone, air and gold inserts. The source consisted in a single seed of 125I (SelectSeed, Nucletron, The Netherlands). Dose distributions were obtained from calculations based on the TG‐43 formalism, from MC simulations (GEANT4 v.9.3) and from a GPU‐based version of the TG‐43 formalism capable of handling heterogeneities. This feature was implemented in the GPU algorithm by computing the equivalent water length travelled through each voxel between the emission site and the dose calculation point. Results: Dose profiles were plotted along heterogeneities to visualize the behavior of each method, with MC simulation as the gold standard. Unsurprisingly, the TG‐43 method overestimated the dose behind high‐density/high‐Z regions with errors in excess of 100% in some cases. The modified TG‐43 algorithm implemented on the GPU algorithm was able to better reproduce MC results, with errors in the range −9.3% to 10.5% behind the same regions. Larger differences occurred for backscattering effects, which are only modeled in the MC method, but only on a limited region (1–2 mm). The TG‐43 formalism provides dose distributions almost instantaneously while MC simulations typically required up to four hours for statistically significant results. The modified TG‐43 GPU algorithm was able to reproduce MC results in approximately four seconds. Conclusions: For complex geometries, the GPU‐based TG‐43 algorithm was shown to provide dose distributions that are closer to those obtained with MC simulations while being significantly faster. This improvement can potentially improve the planning in LDR brachytherapy, where inter‐source attenuation and tissue heterogeneities were shown to influence dosimetric parameters.