Real-world examples of sensitivity failures of the 3%/3mm pass rate metric and published action levels when used in IMRT/VMAT system commissioning

7th International Conference on 3D Radiation Dosimetry

Nelms, B.^1 ; Jarry, G.^2 ; Chan, M.^3 ; Hampton, C.^4 ; Watanabe, Y.^5 ; Feygelman, V.^6

Canis Lupus LLC, Merrimac, WI 53561, United States^1

Hopital Maissoneuve-Rosemont, Montreal, QC H1T 2M4, Canada^2

Memorial Sloan-Kettering Cancer Center, Basking Ridge, NJ 07920, United States^3

Wake Forest Baptist Medical Center, Winston-Salem, NC 27157, United States^4

University of Minnesota, Minneapolis, MN 55455, United States^5

Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL 33612, United States^6

关键词: Acceptance testing;    Delivery chain;    Dose analysis;    False negatives;    Gamma analysis;    Pass rate;    Real-world;    Tight tolerances;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/444/1/012086/pdf
DOI  :  10.1088/1742-6596/444/1/012086

来源: IOP

【 摘 要 】

In IMRT/VMAT system commissioning (as with any system), quality is improved by striving for tight tolerances of stringent metrics of accuracy. For 5 cases, passing rates for 3%/3mm gamma analysis were generated following the TG119 instructions. Subsequently, more stringent/sensitive criteria combined with advanced volumetric dose analysis were applied, and in each case significant systematic errors were clearly identified despite the high 3%/3mm passing rates. In 4 of 5 cases, the error was easily remedied. These real-world examples of observed "false negatives" (insensitivities) point towards the inappropriateness of the 3%/3mm gamma passing rate metric as the basis for acceptance testing/commissioning of the IMRT/VMAT delivery chain.