{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,20]],"date-time":"2025-10-20T18:26:28Z","timestamp":1760984788829,"version":"3.41.2"},"reference-count":13,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2013,4,16]],"date-time":"2013-04-16T00:00:00Z","timestamp":1366070400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"},{"start":{"date-parts":[[2015,9,1]],"date-time":"2015-09-01T00:00:00Z","timestamp":1441065600000},"content-version":"tdm","delay-in-days":868,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["aip.org"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2013,5]]},"abstract":"<jats:sec><jats:title><jats:bold>Purpose:<\/jats:bold><\/jats:title><jats:p>This study presents a follow\u2010up to a modified calibration procedure for portal dosimetry published by Bailey <jats:italic>et al.<\/jats:italic> [\u201cAn effective correction algorithm for off\u2010axis portal dosimetry errors,\u201d Med. Phys. 36, \u2013 (2009) <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"doi\" xlink:href=\"10.1118\/1.3187785\">10.1118\/1.3187785<\/jats:ext-link>]. A commercial portal dose prediction system exhibits disagreement of up to 15% (calibrated units) between measured and predicted images as off\u2010axis distance increases. The previous modified calibration procedure accounts for these off\u2010axis effects in most regions of the detecting surface, but is limited by the simplistic assumption of radial symmetry.<\/jats:p><\/jats:sec><jats:sec><jats:title><jats:bold>Methods:<\/jats:bold><\/jats:title><jats:p>We find that a two\u2010dimensional (2D) matrix correction, applied to each calibrated image, accounts for off\u2010axis prediction errors in all regions of the detecting surface, including those still problematic after the radial correction is performed. The correction matrix is calculated by quantitative comparison of predicted and measured images that span the entire detecting surface. The correction matrix was verified for dose\u2010linearity, and its effectiveness was verified on a number of test fields. The 2D correction was employed to retrospectively examine 22 off\u2010axis, asymmetric electronic\u2010compensation breast fields, five intensity\u2010modulated brain fields (moderate\u2010high modulation) manipulated for far off\u2010axis delivery, and 29 intensity\u2010modulated clinical fields of varying complexity in the central portion of the detecting surface.<\/jats:p><\/jats:sec><jats:sec><jats:title><jats:bold>Results:<\/jats:bold><\/jats:title><jats:p>Employing the matrix correction to the off\u2010axis test fields and clinical fields, predicted vs measured portal dose agreement improves by up to 15%, producing up to 10% better agreement than the radial correction in some areas of the detecting surface. Gamma evaluation analyses (3 mm, 3% global, 10% dose threshold) of predicted vs measured portal dose images demonstrate pass rate improvement of up to 75% with the matrix correction, producing pass rates that are up to 30% higher than those resulting from the radial correction technique alone. As in the 1D correction case, the 2D algorithm leaves the portal dosimetry process virtually unchanged in the central portion of the detector, and thus these correction algorithms are not needed for centrally located fields of moderate size (at least, in the case of 6 MV beam energy).<\/jats:p><\/jats:sec><jats:sec><jats:title><jats:bold>Conclusion:<\/jats:bold><\/jats:title><jats:p>The 2D correction improves the portal dosimetry results for those fields for which the 1D correction proves insufficient, especially in the inplane, off\u2010axis regions of the detector. This 2D correction neglects the relatively smaller discrepancies that may be caused by backscatter from nonuniform machine components downstream from the detecting layer.<\/jats:p><\/jats:sec>","DOI":"10.1118\/1.4800493","type":"journal-article","created":{"date-parts":[[2013,4,16]],"date-time":"2013-04-16T22:07:18Z","timestamp":1366150038000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":6,"title":["A two\u2010dimensional matrix correction for off\u2010axis portal dose prediction errors"],"prefix":"10.1002","volume":"40","author":[{"given":"Daniel W.","family":"Bailey","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lalith","family":"Kumaraswamy","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mohammad","family":"Bakhtiari","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Matthew B.","family":"Podgorsak","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2013,4,16]]},"reference":[{"key":"e_1_2_5_2_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3187785"},{"key":"e_1_2_5_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.radonc.2004.02.018"},{"key":"e_1_2_5_4_1","doi-asserted-by":"publisher","DOI":"10.1259\/bjr\/31573847"},{"key":"e_1_2_5_5_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.2885368"},{"volume-title":"Eclipse Algorithms Reference Guide","year":"2011","author":"Varian Medical Systems Inc.","key":"e_1_2_5_6_1"},{"key":"e_1_2_5_7_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.2779944"},{"key":"e_1_2_5_8_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.2128498"},{"key":"e_1_2_5_9_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3058481"},{"key":"e_1_2_5_10_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3369445"},{"key":"e_1_2_5_11_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.2369465"},{"key":"e_1_2_5_12_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4709602"},{"key":"e_1_2_5_13_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3400043"},{"key":"e_1_2_5_14_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.3651695"}],"container-title":["Medical Physics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1118%2F1.4800493","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1118%2F1.4800493","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/aapm.onlinelibrary.wiley.com\/doi\/pdf\/10.1118\/1.4800493","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,10,5]],"date-time":"2023-10-05T01:12:25Z","timestamp":1696468345000},"score":1,"resource":{"primary":{"URL":"https:\/\/aapm.onlinelibrary.wiley.com\/doi\/10.1118\/1.4800493"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2013,4,16]]},"references-count":13,"journal-issue":{"issue":"5","published-print":{"date-parts":[[2013,5]]}},"alternative-id":["10.1118\/1.4800493"],"URL":"https:\/\/doi.org\/10.1118\/1.4800493","archive":["Portico"],"relation":{},"ISSN":["0094-2405","2473-4209"],"issn-type":[{"type":"print","value":"0094-2405"},{"type":"electronic","value":"2473-4209"}],"subject":[],"published":{"date-parts":[[2013,4,16]]},"article-number":"051704"}}