A framework for implementation of organ effect models in TOPAS with benchmarks extended to proton therapy

Area of Science:

• Medical Physics
• Computational Biology
• Radiotherapy Research

Background:

• Accurate modeling of organ effects is crucial for optimizing particle therapy treatment planning.
• Existing simulation tools require enhanced capabilities for incorporating radiobiological models.

Purpose of the Study:

• To develop and validate a flexible framework for organ effect modeling within the TOPAS (TOol for PArticle Simulation) platform.
• To implement and compare multiple dose-response models for normal tissue and tumor control probability.
• To establish a new benchmark for verifying organ effect models in proton therapy.

Main Methods:

• Extended the DICOM interface of TOPAS to enable organ contour input for voxel assignment.
• Implemented several established dose-response models, including Lyman-Kutcher-Burman, critical element, critical volume, parallel-serial, Niemierko sigmoid, and Poisson models.
• Developed a new benchmark with customized structures for model verification and tested the framework using a Head and Neck patient case.

Main Results:

• The framework demonstrated sensitivity to dose-volume histogram (DVH) point spacing, with variations up to 2.4% compared to AAPM TG166 data.
• Monte Carlo simulations in TOPAS showed differences up to 9% for the parallel-serial model and 0.5% for the Poisson model.
• Significant variations (up to 74.5%) were observed between different organ effect models, highlighting the need for standardized verification.

Conclusions:

• The developed TOPAS framework provides a versatile platform for organ effect modeling in particle therapy.
• A new benchmark is proposed to facilitate the rigorous verification of organ effect models in proton therapy.
• The study underscores the variability among different radiobiological models and the importance of model selection and validation in clinical applications.