{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T14:18:54Z","timestamp":1786976334187,"version":"build-2736575974"},"reference-count":32,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2025,2,4]],"date-time":"2025-02-04T00:00:00Z","timestamp":1738627200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J Applied Clin Med Phys"],"published-print":{"date-parts":[[2025,4]]},"abstract":"Abstract<\/jats:title>\n \n Purpose<\/jats:title>\n This study aimed to evaluate the impact of collimator angle, ball bearing (BB) phantom position, and field size on the accuracy of Winston\u2010Lutz (WL) test\u2013derived radiation isocenters.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n WL tests were performed on four TrueBeam linear accelerators. Fifty\u2010six images (eight gantry angles multiplied by seven collimator angles) were acquired for each WL test. Images with different sets of collimator angles were used to compute the radiation isocenters. The resulting radiation isocenters were correlated with the collimator angles. Then, the BB position and radiation field size were varied for the subsequent WL tests. The calculated BB shifts were compared with the known shifts, and the radiation isocenters were compared between different field sizes.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n The use of a single collimator angle led to errors of as much as 0.4\u00a0mm in the calculated radiation isocenters. Systematic differences were observed between the radiation isocenters derived with collimator angle 0\u00b0 and those derived with 90\u00b0 and\/or 270\u00b0. A commonly used opposing collimator angle pair, 90\u00b0 and 270\u00b0, resulted in a vertical 0.1\u00a0mm offset of the radiation isocenters toward the ceiling. Oblique opposite or mixed collimator angles yielded radiation isocenter errors less than 0.1\u00a0mm. The BB shifts derived from WL tests were less than 0.1\u00a0mm from the known shifts. The radiation isocenters varied by less than 0.1\u00a0mm between field sizes ranging from 2\u00a0\u00d7\u00a02 cm\n 2<\/jats:sup>\n to 20\u00a0\u00d7\u00a020 cm\n 2<\/jats:sup>\n .\n <\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n Oblique opposing collimator angle pairs should be considered to minimize errors in localizing radiation isocenters. Uncertainty in BB positioning could be eliminated if the BB is used as a static reference point in space. The field size had no significant effect on the radiation isocenters. With careful design of WL test parameters and image processing, it is possible to achieve a precision of 0.1\u00a0mm in localizing radiation isocenters using WL tests.<\/jats:p>\n <\/jats:sec>","DOI":"10.1002\/acm2.70000","type":"journal-article","created":{"date-parts":[[2025,2,4]],"date-time":"2025-02-04T21:18:46Z","timestamp":1738703926000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["High\u2010precision localization of radiation isocenter using Winston\u2010Lutz test: Impact of collimator angle, phantom position, and field size"],"prefix":"10.1002","volume":"26","author":[{"given":"Weiliang","family":"Du","sequence":"first","affiliation":[{"name":"Department of Radiation Physics The University of Texas MD Anderson Cancer Center Houston Texas 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