Is a weekly qualitative picket fence test sufficient? A proposed alternate EPID‐based weekly MLC QA program. Issue 8 (20th July 2022)

• Record Type: Journal Article
• Authors: Kalavagunta, Chaitanya; Xu, Huijun; Zhang, Baoshe; Mossahebi, Sina; MacFarlane, Michael; Jiang, Kai; Lee, Sung‐Woo; Chen, Shifeng; Sawant, Amit; Gopal, Arun; Yi, ByongYong
• Is Part Of: Journal of applied clinical medical physics. Volume 23:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-07-20
• Subjects: American Association of Physics in Medicine Task Group 142 -- electronic portal imaging device -- failure mode and effects analysis -- leaf‐end leakage -- multileaf collimator quality assurance -- picket fence -- volumetric‐modulated arc therapy; Medical physics -- Periodicals; Clinical medicine -- Periodicals; Health Physics; Clinical Medicine; Electronic journals; Periodicals; Periodicals; Fulltext; Internet Resources; 610.153
• DOI: 10.1002/acm2.13699
• Languages: English
• ISSNs: 1526-9914

Abstract

Abstract: Purpose: Well‐designed routine multileaf collimator (MLC) quality assurance (QA) is important to assure external‐beam radiation treatment delivery accuracy. This study evaluates the clinical necessity of a comprehensive weekly (C‐Weekly) MLC QA program compared to the American Association of Physics in Medicinerecommended weekly picket fence test (PF‐Weekly), based on our seven‐year experience with weekly MLC QA. Methods: The C‐Weekly MLC QA program used in this study includes 5 tests to analyze: (1) absolute MLC leaf position; (2) interdigitation MLC leaf position; (3) picket fence MLC leaf positions at static gantry angle; (4) minimum leaf‐gap setting; and (5) volumetric‐modulated arc therapy delivery. A total of 20, 226 QA images from 16, 855 tests (3, 371 tests × 5) for 11 linacs at 5 photon clinical sites from May 2014 to June 2021 were analyzed. Failure mode and effects analysis was performed with 5 failure modes related to the 5 tests. For each failure mode, a risk probability number (RPN) was calculated for a C‐Weekly and a PF‐Weekly MLC QA program. The probability of occurrence was evaluated from statistical analyses of the C‐Weekly MLC QA. Results: The total number of failures for these 16, 855 tests was 143 (0.9%): 39 (27.3%) for absolute MLC leaf position, 13 (9.1%) for interdigitation position, 9 (6.3%) for static gantry picket fence, 2 (1.4%) for minimum leaf‐gap setting, and 80 (55.9%) for VMAT delivery. RPN scores for PF‐Weekly MLC QA ranged from 60 to 192 and from 48 to 96 for C‐Weekly MLC QA. Conclusion: RPNs for the 5 failure modes of MLC QA tests were quantitatively determined and analyzed. A comprehensive weekly MLC QA is imperative to lower the RPNs of the 5 failure modes to the desired level (<125); those from the PF‐Weekly MLC QA program were found to be higher (>125). This supports the clinical necessity for comprehensive weekly MLC QA.