{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,7,30]],"date-time":"2025-07-30T07:32:21Z","timestamp":1753860741774,"version":"3.41.2"},"reference-count":28,"publisher":"Wiley","issue":"7","license":[{"start":{"date-parts":[[2023,3,30]],"date-time":"2023-03-30T00:00:00Z","timestamp":1680134400000},"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":[[2023,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Purpose<\/jats:title><jats:p>To assess dynamic tumor tracking (DTT) target localization uncertainty for in\u2010vivo marker\u2010based stereotactic ablative radiotherapy (SABR) treatments of the liver using electronic\u2010portal\u2010imaging\u2010device (EPID) images. The Planning Target Volume (PTV) margin contribution for DTT is estimated.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>Phantom and patient EPID images were acquired during non\u2010coplanar 3DCRT\u2010DTT delivered on a Vero4DRT linac. A chain\u2010code algorithm was applied to detect Multileaf Collimator (MLC)\u2010defined radiation field edges. Gold\u2010seed markers were detected using a connected neighbor algorithm. For each EPID image, the absolute differences between the measured center\u2010of\u2010mass (COM) of the markers relative to the aperture\u2010center (Tracking Error, (E<jats:sub>T<\/jats:sub>)) was reported in pan, tilt, and 2D\u2010vector directions at the isocenter\u2010plane.<\/jats:p><\/jats:sec><jats:sec><jats:title>Phantom study<\/jats:title><jats:p>An acrylic cube phantom implanted with gold\u2010seed markers was irradiated with non\u2010coplanar 3DCRT\u2010DTT beams and EPID images collected. <jats:italic>Patient Study<\/jats:italic>: Eight liver SABR patients were treated with non\u2010coplanar 3DCRT\u2010DTT beams. All patients had three to four implanted gold\u2010markers. In\u2010vivo EPID images were analyzed.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p><jats:italic>Phantom Study<\/jats:italic>: On the 125 EPID images collected, 100% of the markers were identified. The average\u00a0\u00b1\u00a0SD of E<jats:sub>T<\/jats:sub> were 0.24\u00a0\u00b1\u00a00.21, 0.47\u00a0\u00b1\u00a00.38, and 0.58\u00a0\u00b1\u00a00.37\u00a0mm in pan, tilt and 2D directions, respectively. <jats:italic>Patient Study<\/jats:italic>: Of the 1430 EPID patient images acquired, 78% had detectable markers. Over all patients, the average\u00a0\u00b1\u00a0SD of E<jats:sub>T<\/jats:sub> was 0.33\u00a0\u00b1\u00a00.41\u00a0mm in pan, 0.63\u00a0\u00b1\u00a00.75\u00a0mm in tilt and 0.77\u00a0\u00b1\u00a00.80\u00a0mm in 2D directions The random 2D\u2010error, \u03c3, for all patients was 0.79\u00a0mm and the systematic 2D\u2010error, \u03a3, was 0.20\u00a0mm. Using the Van Herk margin formula 1.1\u00a0mm planning target margin can represent the marker based DTT uncertainty.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Marker\u2010based DTT uncertainty can be evaluated in\u2010vivo on a field\u2010by\u2010field basis using EPID images. This information can contribute to PTV margin calculations for DTT.<\/jats:p><\/jats:sec>","DOI":"10.1002\/acm2.13969","type":"journal-article","created":{"date-parts":[[2023,3,30]],"date-time":"2023-03-30T16:56:42Z","timestamp":1680195402000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["In\u2010vivo quality assurance of dynamic tumor tracking (DTT) for liver SABR using EPID images"],"prefix":"10.1002","volume":"24","author":[{"given":"Maryam","family":"Rostamzadeh","sequence":"first","affiliation":[{"name":"Department of Physics and Astronomy University of\u00a0British\u00a0Columbia  Vancouver BC Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kurt","family":"Luchka","sequence":"additional","affiliation":[{"name":"Medical Physics Department BC Cancer\u2010Vancouver  Vancouver 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