Multi-Modality Beam Configuration and Uncertainty Analysis for Hybrid Stereotactic Body Radiotherapy (SBRT) Treatment of Head Neck Cancer
Abstract
Purpose
This study aimed to determine the optimal beam configuration for hybrid SBRT in head and neck cancer by systematically comparing 5, 7, 9, and 11 beam arrangements, with particular emphasis on dosimetric quality, robustness to uncertainties, and clinical feasibility.
Methods
Ten clinically approved head and neck cancer treatment datasets were retrospectively replanned using four distinct beam configurations. Plan quality was evaluated using standard dosimetric metrics, including target dose coverage, Conformity Index, Homogeneity Index , and maximum doses to critical organs at risk, such as the spinal cord, brainstem, parotid glands, and optic structures. To assess plan stability, robustness analyses were performed by introducing setup and dose calculation uncertainties, allowing evaluation of sensitivity to geometric and dosimetric variations across beam configurations.
Results
Among the evaluated configurations, the 9-beam arrangement consistently achieved the most favorable balance between plan quality and clinical efficiency. It demonstrated near-optimal CI and HI values while maintaining reliable OAR sparing across the majority of cases. Lower beam numbers were generally inadequate in anatomically complex scenarios, leading to compromised conformity and suboptimal dose gradients. While the 11-beam configuration provided improved conformity in select cases with highly irregular target geometries, its benefits were not universal and were associated with increased planning and delivery complexity. Robustness analysis confirmed that hybrid beam configurations, particularly the 9-beam setup, exhibited strong resilience to setup and calculation uncertainties.
Conclusion
Based on comprehensive dosimetric evaluation and robustness validation, a 9-beam configuration is recommended as the optimal standard for hybrid SBRT in head and neck cancer. This approach offers an effective balance of precision, safety, and practicality, while selective escalation to 11 beams may be justified for anatomically complex cases. These findings support the development of evidence-based beam selection guidelines and provide a foundation for future integration into adaptive and automated radiotherapy workflows.