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Improved heterogeneity handling in the collapsed cone dose engine for brachytherapy
Freja Alpsten1,2, Bob van Veelen3, Christian Valdes-Cortez4
1Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden.
Medical Physics
|October 29, 2024
Summary
Model-based dose calculation algorithms (MBDCA) like ACE can underestimate dose in non-water media. This study improved the multiple-scatter dose calculation in ACE, enhancing accuracy for bone and other heterogeneities without affecting computation time.
Area of Science:
- Medical Physics
- Radiotherapy
- Computational Dosimetry
Background:
- Model-based dose calculation algorithms (MBDCA) are crucial for overcoming limitations of traditional methods like TG-43 in radiotherapy.
- The Advanced Collapsed Cone Engine (ACE) algorithm, a widely used MBDCA, has shown dose underestimations in non-water media, particularly for cortical bone.
- These inaccuracies are attributed to approximations in calculating the multiple-scatter dose component at greater distances from the source.
Purpose of the Study:
- To enhance the accuracy of the multiple-scatter dose calculation within the ACE algorithm.
- To address and rectify the underestimation of dose in non-water geometries, specifically cortical bone.
- To validate the improved algorithm's performance against established Monte Carlo simulations.
Main Methods:
- A detailed analysis of energy fluence transport and absorption identified an inconsistency in non-water media scaling for the multiple-scatter kernel.
- An updated algorithm, ACEcorr, was developed and implemented to correct this inconsistency.
- ACEcorr was tested using three phantom geometries with a 192Ir source and cortical bone or air heterogeneities, comparing results with ACE and Monte Carlo simulations.
Main Results:
- The ACEcorr algorithm demonstrated superior accuracy compared to the original ACE, significantly improving the mean percentage dose difference in cortical bone.
- In cortical bone, the dose difference improved from to in the worst-case scenario.
- Deviations in air heterogeneities were less than 2% for both algorithms, and calculation times remained unaffected by the update.
Conclusions:
- The implemented updates to the ACE algorithm effectively improved the accuracy of multiple-scatter dose calculations for non-water media.
- The enhanced ACEcorr algorithm provides more reliable dose estimations in complex treatment planning scenarios.
- These improvements were achieved without any increase in computational time, making the updated algorithm practical for clinical use.
