Characterization of a Novel Multi-Functional Daily QA Device for Comprehensive Linear Accelerator Quality Assurance
Abstract
Purpose
Modern radiation therapy incorporates advanced technologies including surface guidance, 6DoF couches, SRS, and combined-axis delivery. Traditional QA programs test these capabilities in isolation using multiple independent phantoms. This work characterizes a novel daily QA device integrating comprehensive beam measurements, mechanical verification, and advanced image-guidance assessment into a single platform.
Methods
A novel fourth-generation multi-detector phantom was commissioned following AAPM TG-312 and tested across seven linear accelerators (five TrueBeam, one Ethos, one Edge). The device contains high-density diode arrays on principle and diagonal axes (with energy wedge), lateral orthogonal arrays, four centrally located diagonal chamber arrays, and eight embedded off-axis fiducials. Characterization included beam parameters (output, flatness, symmetry, energy, profiles) for all photon and electron energies, profile and field size stability (5-20cm jaw/MLC comparison), three-dimensional isocenter assessment using embedded fiducials in comparison to MPC/Winston-Lutz, surface guidance validation, imaging artifact evaluation (CT, CBCT, MVCT), and workflow efficiency analysis.
Results
TG-312 criteria for leakage, array response variation, dose and dose rate linearity, and reproducibility demonstrated maximum dose deviation accuracy of 0.13%, maximum response variation < 0.4% with dose rate. Field size stability deviated <0.5% across multiple field sizes and machines, with MLC-defined fields showing less variation than jaw-defined fields. Radiation field-defined (Active Measurement) isocenter agreement was congruent with MPC and Winston-Lutz methods to within 0.5mm, while image-based WL assessed mechanical/imaging systems in greater detail. Surface guidance displacement accuracy was within 0.2mm/0.2deg. Imaging showed minimal artifacts across modalities. Dose output measurement was slightly faster than previous model generations, with separate radiation and imaging isocenter tests on par with MPC and MMWL times, respectively.
Conclusion
The device successfully consolidates beam dosimetry, IGRT workflows, imaging and radiation isocenter QA, and SGRT testing into a comprehensive platform. Unique transparent interpretable measurements, and efficient workflows enable independent verification per AAPM TG-332 recommendations while enhancing clinical QA programs.