Abstract
The goal of this work was to evaluate the accuracy of our in-house analytical dose calculation code against MCNPX data in heterogeneous phantoms. The analytical model utilizes a pencil beam model based on Fermi-Eyges theory to account for multiple Coulomb scattering and a least-squares fit to Monte Carlo data to account for nonelastic nuclear interactions as well as any remaining, uncharacterized scatter (the 'nuclear halo'). The model characterized dose accurately (up to 1% of maximum dose in broad fields (4 × 4 cm2 and 10 × 10 cm2) and up to 0.01% in a narrow field (0.1 × 0.1 cm2) fit to MCNPX data). The accuracy of the model was benchmarked in three types of stylized phantoms: (1) homogeneous, (2) laterally infinite slab heterogeneities, and (3) laterally finite slab heterogeneities. Results from homogeneous phantoms and laterally infinite slab heterogeneities showed high levels of accuracy (>98% of points within 2% or 0.1 cm distance-to-agreement (DTA)). However, because range straggling and secondary particle production were not included in our model, central-axis dose differences of 2-4% were observed in laterally infinite slab heterogeneities when compared to Monte Carlo dose. In the presence of laterally finite slab heterogeneities, the analytical model resulted in lower pass rates (>96% of points within 2% or 0.1 cm DTA), which was attributed to the use of the central-axis approximation.
Original language | English |
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Pages (from-to) | 1172-1191 |
Number of pages | 20 |
Journal | Physics in medicine and biology |
Volume | 62 |
Issue number | 3 |
DOIs | |
State | Published - Feb 7 2017 |
Keywords
- MCNPX
- Monte Carlo
- dose calculation
- nuclear halo
- pencil beam algorithm
- proton