Commissioning of a reference beam model-based Monte Carlo dose calculation algorithm for cranial stereotactic
Yohan A Walter1, Anne N Hubbard2, Philip F Durham2
1Department of Radiation Oncology, Willis Knighton Cancer Center, 2600 Kings Highway Shreveport, LA 71103, USA; Department of Clinical Research, University of Jamestown, 4190 26th Avenue South Fargo, ND 58104, USA.
Summary
Implementing reference beam models for stereotactic radiosurgery (SRS) treatment planning systems (TPS) significantly reduces commissioning time. This approach ensures accurate Monte Carlo dose calculations and validates system performance for clinical use.
Area of Science:
- Medical Physics
- Radiotherapy
- Computational Dosimetry
Background:
- Treatment planning system (TPS) commissioning for stereotactic radiosurgery (SRS) is complex and time-consuming.
- Brainlab AG has introduced reference beam models for their Elements TPS.
- Accurate beam modeling is crucial for precise dose delivery in SRS.
Purpose of the Study:
- To implement and validate reference beam model-based Monte Carlo dose calculations in the Elements 4.0 TPS.
- To assess the feasibility of reducing measurement burden during TPS commissioning.
- To ensure the accuracy and reliability of dose calculations for SRS.
Main Methods:
- Selected a reference beam model using depth dose, output factor, and beam profile measurements.
- Created 9 treatment plans covering diverse clinical scenarios.
- Performed patient-specific quality assurance (QA) with a high-resolution detector array and independent monitor unit (MU) verifications.
- Conducted end-to-end testing for comprehensive system validation.
Main Results:
- Demonstrated acceptable agreement between measured data and the reference beam model.
- Achieved QA gamma pass rates exceeding 95%.
- Observed peak dose differences over 5% for targets <7 mm diameter at 1.0 mm Monte Carlo grid resolution.
- Found one discrepancy exceeding 5% in MU verification among 46 tested arcs.
Conclusions:
- Validation testing confirmed good agreement for targets ≥7 mm diameter.
- Reference beam models can substantially decrease measurement requirements for TPS commissioning.
- This approach helps mitigate potential failure modes inherent in traditional TPS commissioning processes.
