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A Comprehensive Evaluation of the Performance of the CyberKnife M6: A One-Year Study of Daily QA

J Gersh1,2 , R Fulkerson3*, (1) Gibbs Cancer Center & Research Institute - Pelham, Greer , SC, (2) Spectrum Medical Physics, LLC, Greenville , SC,(3) RKF Consultants, Dundee, NY


(Monday, 7/30/2018) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 7

Purpose: As more efficient CyberKnifeâ„¢ QA devices become commercially available, clinics can implement more comprehensive daily QA procedures. Daily QA results are presented for a 12-month period on a CyberKnifeâ„¢ M6 (Accuray, Inc., Sunnyvale, CA). These data provide a quantitative foundation for considering a reduction of mechanical and dosimetric tolerances (with respect to vendor-recommended and TG-135-recommended tolerances).

Methods: Using the QAStereoChecker and the QABeamChecker+ (Standard Imaging, Inc., Middleton, WI), a daily battery of QA tests were performed that verified output constancy, beam flatness, Irisâ„¢ collimator diameter, target localization accuracy, and leaf positions for the InCiseâ„¢ MLC system across a 12-month period.

Results: The maximum reported deviation in Iris™ diameter was 0.148 mm with an average deviation across all diameters of 0.0177 mm (2σ = 0.0767 mm) from a baseline value. The maximum change in penumbral width of a 60.0 mm Iris™-collimated was 0.516 mm, with an average deviation of 0.021 mm (2σ = 0.174 mm). The maximum change in flatness of that field was 0.502%, with an average deviation of 0.083% (2σ = 0.471 mm). The maximum total localization deviation was 0.516 mm, with an average total deviation of 0.256 mm (2�= 0.161 mm). The maximum deviation in beam output was 1.2%, with an average value of 0.0738% (2σ = 0.783%). Finally, using a daily garden fence analysis, it was found that no leaves’ positions deviated by more than 0.2 mm.

Conclusion: The M6 performed within the mechanical and dosimetric tolerances recommended by TG-135. Since TG-135 pre-dates the InCiseâ„¢ and Irisâ„¢ collimators, these data were compared against the recommended tolerances provided by Accuray. Following an accurate quantification of the dosimetric and mechanical capabilities of this machine, tolerances were narrowed, which can subsequently lead to a reduction in tumor and OAR delineation margins.

Funding Support, Disclosures, and Conflict of Interest: Research Funded In-Part by Standard Imaging, Inc., Middleton, WI.


Radiosurgery, Quality Assurance, Flat-panel Imagers


TH- External beam- photons: cyberknife

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