{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,15]],"date-time":"2025-11-15T11:47:56Z","timestamp":1763207276334,"version":"3.45.0"},"reference-count":17,"publisher":"Wiley","issue":"11","license":[{"start":{"date-parts":[[2025,10,26]],"date-time":"2025-10-26T00:00:00Z","timestamp":1761436800000},"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":[[2025,11]]},"abstract":"Abstract<\/jats:title>\n \n Purpose<\/jats:title>\n This study evaluated the impact of extended field\u2010of\u2010view (eFOV) CT distortion on the alignment accuracy of surface\u2010guided radiation therapy (SGRT) using CT\u2010based reference surfaces, and examined the influence of beam center location.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n An anthropomorphic phantom, segmented into chest, abdomen, and pelvis, was scanned at the center position (sFOV) and at four off\u2010center positions. The center corresponds to the CT bore isocenter, while the off\u2010center positions were obtained by placing the phantom boundary 315 mm or 390 mm to the left or right of the CT isocenter to simulate eFOV conditions. Geometric distortion was assessed by measuring external body contour volume. Treatment plans were generated with beam centers at the isocenter and at off\u2010center positions of 8 cm left and right. SGRT registration accuracy was evaluated from SGRT alignment error and cone\u2010beam CT (CBCT) alignment error differences using axis\u2010specific mean absolute errors (MAEs) and overall translational and rotational root mean square errors (RMSEs).<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n Distortion was most pronounced in the chest when the phantom boundary was 390 mm right of the isocenter, with a 12.55% volume reduction. In contrast, abdomen and pelvis volume changes were within 1% across all positions. At the isocenter, MAEs increased at 390 mm off\u2010center positions, with chest showing lateral\/vertical errors and abdomen exhibiting longitudinal\/rotational deviations. When the beam center was 8 cm lateral and adjacent to a distorted region, errors increased, while contralateral placement showed errors comparable to the isocenter. Maximum RMSEs of 10.98 mm (translation) and 5.88\u00b0 (rotation) occurred in the abdomen when beam centers overlapped distorted regions, exceeding typical clinical thresholds (5 mm, 2\u00b0). The pelvis showed relatively stable alignment with RMSEs within 2.5 mm and 1.5\u00b0.<\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n This phantom study demonstrated that eFOV reconstruction can compromise SGRT alignment accuracy, particularly when beam centers are located near distorted regions. Alignment remained within clinically acceptable limits when reference points were sufficiently distant from distortion. These findings provide important baseline data under controlled conditions, and clinical validation with patient cohorts is warranted to confirm their generalizability.<\/jats:p>\n <\/jats:sec>","DOI":"10.1002\/acm2.70312","type":"journal-article","created":{"date-parts":[[2025,10,27]],"date-time":"2025-10-27T05:11:37Z","timestamp":1761541897000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Impact of eFOV CT distortion on surface\u2010guided radiotherapy registration: Phantom\u2010based analysis"],"prefix":"10.1002","volume":"26","author":[{"given":"Wooseok","family":"Kim","sequence":"first","affiliation":[{"name":"Department of Radiation Oncology Pohang St. Mary's Hospital Pohang\u2010si Gyeongsangbuk\u2010do Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hyunsoo","family":"Jang","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology Pohang St. Mary's Hospital Pohang\u2010si Gyeongsangbuk\u2010do Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eng Chan","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Physics Yeungnam University Gyeongsan\u2010si Gyeongsangbuk\u2010do Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jonggeun","family":"Baek","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology Dongguk University Gyeongju Hospital Gyeongju\u2010si Gyeongsangbuk\u2010do Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Byungyong","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology Keimyung University Dongsan Hospital Dalseo\u2010gu Daegu Republic of 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