{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T14:50:16Z","timestamp":1786978216193,"version":"build-2736575974"},"reference-count":36,"publisher":"Wiley","issue":"12","license":[{"start":{"date-parts":[[2025,12,8]],"date-time":"2025-12-08T00:00:00Z","timestamp":1765152000000},"content-version":"vor","delay-in-days":7,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2025,12,1]],"date-time":"2025-12-01T00:00:00Z","timestamp":1764547200000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2025,12]]},"abstract":"Abstract<\/jats:title>\n \n Background<\/jats:title>\n Real\u2010time tumor tracking (RTTT) is an effective strategy for managing respiratory motion during radiation therapy; however, it typically requires invasive fiducial markers. As a non\u2010invasive alternative, markerless RTTT (ML\u2010RTTT) has gained increasing interest, especially with the growing use of volumetric modulated arc therapy (VMAT), which requires efficient real\u2010time motion compensation.<\/jats:p>\n <\/jats:sec>\n \n Purpose<\/jats:title>\n This study aimed to develop and evaluate a tumor position estimation algorithm for ML\u2010RTTT integrated with VMAT (ML\u2010RTTT\u2010VMAT), using the diaphragm dome projection as a surrogate, with an added method to compensate for phase\u2010dependent asynchrony between diaphragm and tumor motion.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n The analysis included 43 sessions performed on 23 patients whose tumors exhibited motion greater than 10 mm and who had fiducial markers implanted near the tumors. Rotational kV x\u2010ray images were acquired from two orthogonal directions during free breathing. Infrared reflective (IR) markers were placed on the abdomen near or above the umbilicus to track respiratory motion. Diaphragm templates were generated from planning CT images, and diaphragm positions were identified by template matching with epipolar geometry. The 3D diaphragm dome position was computed via triangulation. The initial 20\u00a0s of each session were used to build a prediction model linking the IR marker signal to tumor position. Tumor position was approximated using the centroid of the implanted fiducial markers (pseudo tumor). Three scenarios were evaluated: (i) S\n no<\/jats:sub>\n , a baseline scenario assuming direct availability of the pseudo\u2010tumor position without diaphragm detection or offset\u2010vector estimation; (ii) S\n con<\/jats:sub>\n , a constant offset vector defined at an end\u2010expiratory phase and applied to all phases; and (iii) S\n var<\/jats:sub>\n , a variable offset vector dependent on respiratory phase. The model was validated using the remaining 50\u00a0s of data, and the prediction accuracy of each model was assessed using the 90th percentile error (\n E<\/jats:italic>\n 90<\/jats:sub>\n ) in each direction.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n The\n E<\/jats:italic>\n 90<\/jats:sub>\n values for left\u2013right, superior\u2013inferior, and anterior\u2013posterior directions were as follows: S\n no<\/jats:sub>\n : 2.4, 4.1, and 4.0 mm; S\n con<\/jats:sub>\n : 2.7, 5.7, and 4.5 mm; and S\n var<\/jats:sub>\n : 2.3, 4.5, and 3.7 mm. Large errors were observed in six sessions (14.0% of all S\n var<\/jats:sub>\n sessions), mainly due to irregular respiratory patterns or pulsation artifacts in the IR marker signal.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n The proposed ML\u2010RTTT\u2010VMAT approach using diaphragm\u2010based prediction with a phase\u2010dependent offset vector is feasible and holds promise for markerless real\u2010time motion management in radiation therapy.<\/jats:p>\n <\/jats:sec>","DOI":"10.1002\/mp.70190","type":"journal-article","created":{"date-parts":[[2025,12,9]],"date-time":"2025-12-09T02:54:49Z","timestamp":1765248889000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Feasibility of markerless real\u2010time tumor tracking volumetric modulated arc therapy using diaphragm\u2010based respiratory offset vectors"],"prefix":"10.1002","volume":"52","author":[{"given":"Yukine","family":"Shimizu","sequence":"first","affiliation":[{"name":"Department of Advanced Medical Physics Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Noriko","family":"Kishi","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology and Image\u2010Applied Therapy Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takashi","family":"Mizowaki","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology and Image\u2010Applied Therapy Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mitsuhiro","family":"Nakamura","sequence":"additional","affiliation":[{"name":"Department of Advanced Medical Physics Graduate School of Medicine Kyoto University Kyoto 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