Comparison of dose distributions for Hounsfield number conversion methods in GEANT4
- Comparison of dose distributions for Hounsfield number conversion methods in GEANT4
- 김성규; 김형동; 김응찬; 김병용; 강정구 [강정구 ]; 윤상모[윤상모]
- MONTE-CARLO SIMULATIONS; CT NUMBERS; TISSUE PARAMETERS; PHOTON; VALIDATION; TOOLKIT; PHYSICS; NOZZLE
- Issue Date
- KOREAN PHYSICAL SOC
- JOURNAL OF THE KOREAN PHYSICAL SOCIETY, v.64, no.12, pp.1912 - 1918
- The conversion of patient computed tomography (CT) data to voxel phantoms is essential for CT-based Monte Carlo (MC) dose calculations, and incorrect assignments of materials and mass densities can lead to large errors in dose distributions. We investigated the effects of mass density and material assignments on GEANT4-based photon dose calculations. Three material conversion methods and four density conversion methods were compared for a lung tumor case. The dose calculations for 6-MV photon beams with a field size of 10 x 10 cm(2) were performed using a 0.5 x 0.5 x 0.5 cm(3) voxel with 1.2 x 10(9) histories. The material conversion methods led to different material assignment percentages in converted voxel regions. The GEANT4 example and the modified Schneider material conversion methods showed large local dose differences relative to the BEAMnrc default method for lung and other tissues. For mass density conversion methods when only water was used, our results showed only slight dose differences. Gaussian-like distributions, with mean values close to zero, were obtained when the reference method was compared with the other methods. The maximum dose difference of similar to 2% indicated that the dose distributions agreed relatively well. Material assignment methods probably have more significant impacts on dose distributions than mass density assignment methods. The study confirms that material assignment methods cause significant dose differences in GEANT4-based photon dose calculations.
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