Benchmark performance measurements of a novel biology-guided radiotherapy (BgRT) machine using TG-148 and TG-142
D. Zaks,1 R. Bassalow,2 O. Volotskova,3 M. Narayanan,1 C. Huntzinger,1 S. Shirvani,1 S. Mazin,1 G. Kuduvalli1
1RefleXion Medical, Hayward, CA; 2Northwest Medical Physics Center, Silverdale, WA; 3Sutter Health, Berkeley, CA
AAPM/COMP Annual Scientific Meeting, Virtual (2020).
Purpose: To benchmark the mechanical performance of the RefleXion™ X1 biology-guided radiotherapy (BgRT) machine, which employs a novel architecture with linac, kVCT and PET subsystems in the same treatment gantry, using TG-148 and TG-142 methodologies.
Methods: Measurements were executed with adherence to AAPM TG-148 section V.B. methodology, with modification allowed for meaningful differences in machine geometry. Six tests were executed using Red Virtual Water Phantoms (RVWP) from Standard Imaging Inc and XRQA2 film from Ashland Gafchromic. Phantoms were scanned using an EPSON 12000XL-PH flatbed scanner and analyzed using an RITG148+ QA module. The X alignment of MLC to source test was executed using MV EPID images and an in-house Python script to determine the out of focus parameter. The Y jaw alignment to source test was executed using an Exradin A17 ion chamber, using smaller jaw sweep steps due to a smaller range of jaw sweep motion. Finally, a “star shot” test was delivered to XRQA2 film and solid water phantoms to evaluate isocenter size per AAPM TG-142.
Results: All measured parameters passed the evaluated criteria established in TG-148 and TG-142, including Y-jaw twist (0.04° measured vs. 0.5°), Y-jaw divergence (0.48 mm measured vs 0.5 mm), Y-jaw alignment (0.14 mm baseline), MLC twist (0.04° measured vs. 0.5°), MLC Offset (0.39 mm measured vs 1.5 mm), MLC x-alignment (0.21% measured vs 2%), treatment field centering (0.1 mm measured vs 0.5 mm), synchronicity (0.083 mm per 5 cm measured vs 1 mm per 5 cm), and radiation isocenter radius (0.56 mm measured vs 1.0 mm)
Conclusion: The experimental results demonstrated that the novel architecture of the RefleXion X1 machine was able to meet the expected mechanical performance requirements outlined in AAPM TG-148 and TG-142 reports.