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[Electron fields in clinical application. A comparison of pencil beam and Monte Carlo algorithm]
Marius Treutwein1, Ludwig Bogner
1Klinik und Poliklinik für Strahlentherapie--Medizinische Physik, Regensburg University Medical Center, Regensburg. marius.treutwein@klinik.uni-regensburg.de
Monte Carlo algorithms offer more accurate electron dose calculations than pencil beam algorithms, especially for bone inhomogeneities. Pencil beam algorithms are acceptable for chest wall irradiations, but Monte Carlo is preferred for vertebral column treatments.
Area of Science:
- Medical Physics
- Radiation Oncology
- Computational Dosimetry
Background:
- Three-dimensional treatment planning systems commonly use pencil beam algorithms for electron field calculations.
- Exact Monte Carlo methods are now available and demonstrate strong agreement with experimental data.
Purpose of the Study:
- To compare dose distribution differences between pencil beam and Monte Carlo algorithms in clinical electron beam radiotherapy.
- To evaluate the clinical applicability of both algorithms in specific treatment scenarios.
Main Methods:
- Dose distributions were calculated using pencil beam (Helax TMS) and Monte Carlo (VMC++) algorithms for two clinical cases: chest wall irradiation and vertebral column irradiation.
- Depth dose curves and profiles were analyzed using the Verisoft program.
Main Results:
- For chest wall irradiation, depth dose curves showed good agreement between both algorithms, with a mean lung dose difference of only 4%.
- For vertebral column irradiation, a significant dose difference was observed, with the Monte Carlo plan showing 56% lower dose in the prevertebral region compared to the pencil beam calculation.
Conclusions:
- Pencil beam algorithms are suitable for dose calculations in chest wall irradiations.
- The Monte Carlo algorithm is recommended for electron dose distribution calculations involving significant bone inhomogeneities, such as in vertebral column treatments.
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