An integrated toolkit for structure generation, optimization, and evaluation in spatially fractionated radiation...

Spatially fractionated radiation therapy (SFRT) planning requires three coordinated tasks: generation of high-dose sphere structures, position-aware optimization, and peak-valley dose ratio evaluation. In practice, clinicians and researchers address these tasks with a combination of closed-source scripts, research codes, and manual calculation. The absence of a unified, commercially deployable toolkit remains a barrier to multi-institutional SFRT trials. We present MAAS-SFRThelper, a shared-source plugin that integrates structure generation, geometric-aware optimization, and peak-valley dose ratio evaluation for SFRT into a single workflow inside Varian's Eclipse treatment planning system.

MAAS-SFRThelper is a Windows Presentation Foundation (WPF) application built on the Model-View-ViewModel (MVVM) pattern, implemented in C# against ESAPI for Eclipse 15.6 and later. The plugin currently contains five task-oriented tabs that share common services for sphere extraction and objective creation. The SphereLattice tab generates sphere lattices using five placement patterns: hexagonal close-packed, simple cubic, alternating cubic, centroidal Voronoi tessellation, and a constraint-based Monte Carlo method. The SCART tab creates contracted spindle-like boost volumes for stereotactic central ablative radiation therapy. The Optimization tab auto-populates structure list, searches over candidate lattice positions using a four-metric geometric surrogate score, and triggers Eclipse VMAT optimization along with dose calculation on the best candidate. The Evaluation tab implements four analysis modes including 1D, 2D, and 3D PVDR analysis. We validated all functionality on digital phantoms against analytic ground truth. In phantom testing, the optimized lattice achieved 22.5% higher PVDR.

The plugin is distributed as source code that compiles to a single dynamic-link library (DLL); all third-party dependencies are bundled at build time. At first launch, users review the Varian Limited Use Software License Agreement (LUSLA) and enter an access code that is emailed upon request. The plugin accepts the patient structure set and, where applicable, a plan with calculated dose; outputs include new structures written directly to the structure set through ESAPI and summary statistics exported as comma-separated value (CSV) files. Source code and documentation are publicly available on GitHub under the LUSLA.

MAAS-SFRThelper supports clinical lattice SFRT planning with consistent workflows across institutions and standardized peak-valley dose ratio reporting for multi-institutional trials. The shared-services architecture enables community contributions of new placement patterns, evaluation metrics, and validation datasets. These features represent a practical step toward the dosimetric consistency called for in the 2024 NRG Oncology/AAPM consensus on SFRT. The plugin also serves as a platform for research extensions to GRID therapy, minibeam radiation therapy, and other heterogeneous dose-delivery modalities.