Benchmarking a New Paradigm: Commissioning and Validation of the First Ultra-Compact Upright Proton Therapy System
Abstract
Purpose
Commissioning and performance validation of the world’s first ultra-compact upright proton therapy system and establish benchmarks for this novel treatment delivery paradigm.
Methods
TPS Beam model was built and validated with the measured integral depth doses (IDDs), spot profiles in air, virtual SAD, and absolute dose calibration. The system dosimetric performance was validated through spot position accuracy, beam profiles, field penumbra, pristine/SOBP absolute doses, and patient-specific QA. Mechanical and radiation isocentricity, laser alignment, aperture and nozzle accuracy were assessed. 6D positioning accuracy, positioning repeatability, and treatable volume were performed as parts of the UPP evaluation. CT quality was characterized via HU uniformity, low/high contrast resolution, CT number accuracy, imaging dose and CT-RSP calibration. Comprehensive end-to-end tests for different phantoms were performed to evaluate the overall accuracy of the system.
Results
The range agreements (R90 and R80) between TPS and measurements were within 0.14 mm across 59.1–227.1 MeV with distal falloff deviations ≤0.22 mm. Spot size agreement was within 0.23 mm for all energies. Absolute dose calibration agrees with TPS within 0.2%. Absolute dose validation for mono-energetic layers and SOBP fields remained within 1.5% and 2.7%, respectively. Patient-specific QA gamma pass rates were 90.5–96.8% (3%/3mm) and 88.3–94.7% (2%/2mm). Accelerator characterization confirmed spot position accuracy within 0.5 mm over a 20×20 cm² field. Aperture leakage was <1.2% with negligible non-primary radiation (<0.01%). Mechanical integrity showed nozzle/laser deviations ≤0.15 mm. The UPP maintained high precision with linear deviations ≤0.05 mm and rotational accuracy within 0.3°. Upright CT imaging met all clinical requirements in terms of image quality and dose, as well as CT-RSP fidelity.
Conclusion
The first ultra-compact upright proton system was successfully commissioned and validated with overall mechanical and dosimetric accuracy comparable to the conventional gantry systems, offering a unique opportunity to bring PT to a standard photon Linac vault.