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Comparison of dose calculation algorithms with Monte Carlo methods for photon arcs
James C L Chow1, Eugene Wong, Jeff Z Chen
1Department of Physics, London Regional Cancer Center, 790 Commissioners Road East, London, ON N6A 4L6, Canada. james.chow@grhosp.on.ca
Medical Physics
|November 5, 2003
Summary
Monte Carlo simulations accurately calculate photon arc dose distributions, outperforming commercial systems in lung inhomogeneity. This research offers an efficient and precise method for radiation therapy planning.
Area of Science:
- Medical Physics
- Radiation Oncology
- Computational Dosimetry
Background:
- Accurate dose calculation is crucial for effective radiation therapy.
- Photon arc therapy requires precise dose distribution assessment.
- Evaluating different algorithms for photon arc dosimetry is essential.
Purpose of the Study:
- To compare the accuracy and efficiency of Monte Carlo, pencil beam kernel (PK), and collapsed cone convolution (CCC) algorithms for photon arc dose calculation.
- To validate computational methods against experimental measurements in various phantom setups.
Main Methods:
- Monte Carlo simulations using EGS4/DOSXYZ (MCPHS and MCDIV variants) were performed.
- Commercial treatment planning system algorithms (ETAR, PK, CCC) were used for comparison.
- Dose distributions were measured using an ion chamber and radiographic films in PMMA, water, and lung-inhomogeneous phantoms.
Main Results:
- Monte Carlo simulations (MCPHS, MCDIV) showed excellent agreement (approx. 2% error) with measurements for homogeneous phantoms and full arcs (180/360 degrees).
- In lung inhomogeneity with a 90-degree arc, Monte Carlo methods agreed within 2% of measurements.
- Commercial algorithms (ETAR, PK, CCC) exhibited significant dose discrepancies (6-12%) within the lung inhomogeneity.
Conclusions:
- Monte Carlo simulations provide a highly accurate and efficient method for calculating photon arc dose distributions.
- Commercial treatment planning systems may require improvements for accurate dose calculation in complex, inhomogeneous tissues during arc therapy.
- The findings support the use of advanced Monte Carlo methods in clinical photon arc dosimetry.