Automated Whole‑Breast Radiotherapy Planning for a Ring‑Gantry Accelerator (Halcyon) - a Feasibility Study
Abstract
Purpose
The aim of this study was to assess the feasibility of automated left-sided whole‑breast radiotherapy planning for Halcyon (Siemens Healthineers), and to evaluate plan quality against national clinical guidelines.
Methods
Using the Eclipse Scripting API (Siemens Healthineers), automated workflows were developed to generate whole‑breast treatment plans on Halcyon based on the FAST‑Forward fractionation (5fx × 5.2Gy). The plans comprised of two tangential IMRT-fields and two short (30/40°) VMAT-arcs. As part of the automated workflow, gantry angles were optimized to minimize beams-eye-view overlap between the PTV and organs at risk. The pipeline further automated application of skin flash to the IMRT-fields and assignment of optimization objectives. Optimization was performed sequentially, using the IMRT plan (≈85-95% of the total dose) as the base plan for VMAT optimization. A large IMRT proportion and short arcs limited the irradiated volume. Three patient CT datasets in deep inspiration were used to evaluate the automated workflow. Treatment plan quality was evaluated against the national breast radiotherapy protocol, which is more conservative than the original trial protocol, and robustness of target dose coverage (D98%≥95%) was assessed with respect to setup uncertainties (5mm).
Results
The main steps in the generation of hybrid IMRT/VMAT plans were successfully automated. All plans fulfilled the constraints of the clinical protocol. For all plans, V1.3Gy for the heart was below 20% and V7.8Gy for the lung was below 15%. All plans were robust to the simulated uncertainties.
Conclusion
Automated whole‑breast radiotherapy planning for Halcyon was feasible and yielded high‑quality plans, demonstrating proof of concept. Full end‑to‑end automation was limited by the absence of proprietary, scriptable Eclipse functionalities, requiring manual creation of VMAT-arcs and assignment of base‑plan and heart no‑entry/exit constraints. The forthcoming study will include additional enhancements, an expanded patient cohort and pairwise comparisons with alternative planning strategies.