{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T09:43:27Z","timestamp":1790675007684,"version":"4.1.0"},"reference-count":33,"publisher":"Wiley","issue":"2","license":[{"start":{"date-parts":[[2019,12,29]],"date-time":"2019-12-29T00:00:00Z","timestamp":1577577600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2020,2]]},"abstract":"<jats:sec><jats:title>Purpose<\/jats:title><jats:p>With advance magnetic resonance (MR)\u2010guided online adaptive radiotherapy (MRgoART) relying on calculation\u2010based intensity\u2010modulated radiation therapy (IMRT) quality assurance (QA), accurate and sensitive QA of the multileaf collimator (MLC) becomes an increasingly essential component for routine machine QA. As such, it is important to assure compliance with the AAPM TG142 guidelines to supplement calculation\u2010based QA methods for an online adaptive radiotherapy program. We have developed and implemented an efficient and highly sensitive QA procedure using an ionization chamber profiler (ICP) array to enable real\u2010time characterization of the positional accuracy of a double\u2010focused and double\u2010stacked MLC on a clinical MR\u2010guided radiotherapy (MRgRT) system and to supplement calculation\u2010based QA for an MRgoART program.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>An in\u2010house MR\u2010compatible jig was used to position the ICP (detector resolution 5\u00a0mm on X\/Y axis) at an extended SDD of 108.4\u00a0cm to enable each MLC leaf (8.3\u00a0mm leaf width at isocenter) to be uniquely determined by two neighboring ion chambers. The MRgRT linac system utilizes a novel jawless, double\u2010focused, and double\u2010stacked MLC design such that the upper bank (MLC1) and lower bank (MLC2) are offset by half a leaf width. Positional accuracy was characterized by three methods: single bank half\u2010beam block (HBB) at central axis, forward slash diagonal (FSD), and backslash diagonal (BSD) at off\u2010axis. Measurements were performed for each bank in which each leaf occludes half of a detector. A corresponding reference field with the MLC retracted from occlusion was measured. The sensitivities of HBB, FSD, and BSD were evaluated by introducing 0.5\u20132.5\u00a0mm of known errors in 0.5\u00a0mm increments, in both positive and negative directions. The relationship between detector response and MLC error was established. Over a 6\u2010month longitudinal assessment, we have evaluated MLC performance with weekly QA of HBB among cardinal angles, and monthly QA of FSD and BSD.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>A strong correlation was found between detector response of percentage dose difference and MLC positional error introduced (N\u00a0=\u00a0350 introduced errors) for both HBB and FSD\/BSD with coefficient of determination of 0.999 and 0.977, respectively. The relationship between detector response to MLC positional change was found to be 20.65%\/mm for HBB and 11.14%\/mm for FSD and BSD. At baseline, the mean MLC positional accuracy averaged across all leaves was 0.06\u00a0\u00b1\u00a00.27\u00a0mm (HBB), 0.04\u00a0\u00b1\u00a00.52\u00a0mm (FSD), \u22120.06\u00a0\u00b1\u00a00.51\u00a0mm (BSD). The mean MLC positional accuracy relative to baseline over the 6\u2010month assessment was found to be highly reproducible at 0.00\u00a0\u00b1\u00a00.12\u00a0mm (HBB; N\u00a0=\u00a028\u00a0weeks), \u22120.02\u00a0\u00b1\u00a00.19\u00a0mm (FSD; N\u00a0=\u00a06\u00a0months), \u22120.03\u00a0\u00b1\u00a00.19\u00a0mm (BSD; N\u00a0=\u00a06\u00a0months).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Positional accuracy of a novel jawless, double\u2010focused, double\u2010stacked MLC has been characterized and monitored over 6 months with an efficient, highly sensitive, and robust method using an ICP array. This routine QA method supplements calculation\u2010based IMRT QA for an online adaptive radiotherapy program. Longitudinal assessment demonstrated no\u2010drift in the MLC calibration. A highly reproducible jig setup allowed the validation of MLC positional accuracy to be within TG142 criteria of \u00b11\u00a0mm for 99% of measurements (i.e., 100% HBB, 95% BSD, 95% FSD) over the 6\u2010month assessment.<\/jats:p><\/jats:sec>","DOI":"10.1002\/mp.13902","type":"journal-article","created":{"date-parts":[[2019,11,4]],"date-time":"2019-11-04T13:28:51Z","timestamp":1572874131000},"page":"317-330","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["Characterization of positional accuracy of a double\u2010focused and double\u2010stack multileaf collimator on an MR\u2010guided radiotherapy (MRgRT) Linac using an IC\u2010profiler array"],"prefix":"10.1002","volume":"47","author":[{"given":"Kathryn E.","family":"Mittauer","sequence":"first","affiliation":[{"name":"Department of Radiation Oncology Miami Cancer Institute Baptist Health South Florida Miami FL USA"},{"name":"Department of Human Oncology School of Medicine and Public Health University of Wisconsin\u2010Madison Madison WI USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Poonam","family":"Yadav","sequence":"additional","affiliation":[{"name":"Department of Human Oncology School of Medicine and Public Health University of Wisconsin\u2010Madison Madison WI USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bhudatt","family":"Paliwal","sequence":"additional","affiliation":[{"name":"Department of Human Oncology School of Medicine and Public Health University of Wisconsin\u2010Madison Madison WI USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"John E.","family":"Bayouth","sequence":"additional","affiliation":[{"name":"Department of Human Oncology School of Medicine and Public Health University of Wisconsin\u2010Madison Madison WI USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2019,12,29]]},"reference":[{"key":"e_1_2_8_2_1","volume-title":"Image Guidance in Radiation Therapy: Techniques, Accuracy, and Limitations","author":"Hill PM","year":"2018"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1120\/jacmp.v10i1.2905"},{"key":"e_1_2_8_4_1","unstructured":"MittauerKE HillPM BassettiMF BayouthJE.Validation of an MR\u2010Guided Online Adaptive Radiotherapy (MRgoART) Program: Deformation Accuracy in a Heterogeneous Deformable Anthropomorphic Phantom. 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