{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,3]],"date-time":"2026-10-03T00:11:50Z","timestamp":1790986310702,"version":"4.1.0"},"reference-count":44,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2025,1,23]],"date-time":"2025-01-23T00:00:00Z","timestamp":1737590400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Product Evaluation Agreement with Varian Medical Systems"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Current Oncology"],"abstract":"<jats:p>Ethos adaptive radiotherapy is employed frequently in the pelvis to improve treatment accuracy by adapting to daily anatomical changes. The use of this CBCT-guided platform for abdominal treatments is made challenging by motion-related image artifacts that are detrimental to the Ethos auto-contouring process. We present a preliminary in silico study enabled by synthetic CBCT data of Ethos adaptive radiotherapy for pancreatic cancer. Simulation CT and daily CBCT images were collected from nonadaptive patients treated on Ethos. Contoured CBCTs drove structure-guided deformable registration from the CT to daily CBCTs, providing an approximate daily CT used to produce synthetic CBCT data. Two adaptive workflows were simulated using an Ethos emulator. Over 70 fractions across 10 patients in a solely deformation-based workflow, PTV prescription coverage increased by 23.3\u00b19.4% through plan adaptation. Point doses to the stomach were reduced by 10.2\u00b19.3%. Ultimately, un-adapted plans satisfied target coverage and OAR constraints in 0% and 6% of fractions while adapted plans did so in 80% of fractions. Anatomical variation led to poor performance in rigidly aligned un-adapted plans, illustrating the promise of Ethos adaptive radiotherapy in this region. This promise is balanced by the need for artifact reduction and questions regarding auto-contouring performance in the abdomen.<\/jats:p>","DOI":"10.3390\/curroncol32020060","type":"journal-article","created":{"date-parts":[[2025,1,23]],"date-time":"2025-01-23T05:49:54Z","timestamp":1737611394000},"page":"60","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Evaluating CBCT-Guided Adaptive Radiotherapy for Pancreatic Cancer Using Synthetic CBCT Data"],"prefix":"10.3390","volume":"32","author":[{"given":"Sven","family":"Olberg","sequence":"first","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Leah L.","family":"Thompson","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hannah J.","family":"Roberts","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jennifer Y.","family":"Wo","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Theodore S.","family":"Hong","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"John","family":"Wolfgang","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Clemens","family":"Grassberger","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, University of Washington, Seattle, WA 98195, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0531-6798","authenticated-orcid":false,"given":"Jennifer","family":"Pursley","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA 02114, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,1,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1016\/j.ijrobp.2015.10.015","article-title":"Online Magnetic Resonance Image Guided Adaptive Radiation Therapy: First Clinical Applications","volume":"9","author":"Acharya","year":"2016","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"485","DOI":"10.1016\/j.adro.2017.05.006","article-title":"Two-and-a-half-year clinical experience with the world\u2019s first magnetic resonance image guided radiation therapy system","volume":"2","author":"Henke","year":"2017","journal-title":"Adv. Radiat. Oncol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1086","DOI":"10.1016\/j.ijrobp.2019.08.007","article-title":"A Prospective Single-Arm Phase 2 Study of Stereotactic Magnetic Resonance Guided Adaptive Radiation Therapy for Prostate Cancer: Early Toxicity Results","volume":"105","author":"Bruynzeel","year":"2019","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.phro.2020.12.004","article-title":"Clinical implementation of artificial intelligence-driven cone-beam computed tomography-guided online adaptive radiotherapy in the pelvic region","volume":"17","author":"Sibolt","year":"2021","journal-title":"Phys. Imaging Radiat. Oncol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1054","DOI":"10.1016\/j.ijrobp.2020.10.021","article-title":"Adaptive Radiation Therapy (ART) Strategies and Technical Considerations: A State of the ART Review From NRG Oncology","volume":"109","author":"Lee","year":"2021","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1002\/acm2.13425","article-title":"Initial analysis of the dosimetric benefit and clinical resource cost of CBCT-based online adaptive radiotherapy for patients with cancers of the cervix or rectum","volume":"22","author":"Yock","year":"2021","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1002\/acm2.13399","article-title":"Prospects for daily online adaptive radiotherapy via ethos for prostate cancer patients without nodal involvement using unedited CBCT auto-segmentation","volume":"22","author":"Moazzezi","year":"2021","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e13479","DOI":"10.1002\/acm2.13479","article-title":"Varian ethos online adaptive radiotherapy for prostate cancer: Early results of contouring accuracy, treatment plan quality, and treatment time","volume":"23","author":"Byrne","year":"2022","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1016\/j.tipsro.2022.04.001","article-title":"Evaluation of an automated template-based treatment planning system for radiotherapy of anal, rectal and prostate cancer","volume":"22","author":"Calmels","year":"2022","journal-title":"Tech. Innov. Patient Support Radiat. Oncol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e13783","DOI":"10.1002\/acm2.13783","article-title":"Dosimetric and feasibility evaluation of a CBCT-based daily adaptive radiotherapy protocol for locally advanced cervical cancer","volume":"24","author":"Branco","year":"2023","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_11","first-page":"100596","article-title":"Implementing cone-beam computed tomography-guided online adaptive radiotherapy in cervical cancer","volume":"40","author":"Shelley","year":"2023","journal-title":"Clin. Transl. Radiat. Oncol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1016\/j.clon.2018.08.001","article-title":"Adaptive Radiotherapy Enabled by MRI Guidance","volume":"30","author":"Hunt","year":"2018","journal-title":"Clin. Oncol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1111\/1754-9485.12968","article-title":"Magnetic resonance-guided radiation therapy: A review","volume":"64","author":"Chin","year":"2020","journal-title":"J. Med. Imaging Radiat. Oncol."},{"key":"ref_14","first-page":"72","article-title":"4D-MRI driven MR-guided online adaptive radiotherapy for abdominal stereotactic body radiation therapy on a high field MR-Linac: Implementation and initial clinical experience","volume":"23","author":"Paulson","year":"2020","journal-title":"Clin. Transl. Radiat. Oncol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1016\/j.radonc.2019.01.030","article-title":"Modeling daily changes in organ-at-risk anatomy in a cohort of pancreatic cancer patients","volume":"134","author":"Loi","year":"2019","journal-title":"Radiother. Oncol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"3066","DOI":"10.1002\/mp.16305","article-title":"A model for gastrointestinal tract motility in a 4D imaging phantom of human anatomy","volume":"50","author":"Subashi","year":"2023","journal-title":"Med. Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1078","DOI":"10.1016\/j.ijrobp.2016.08.036","article-title":"Simulated Online Adaptive Magnetic Resonance\u2014Guided Stereotactic Body Radiation Therapy for the Treatment of Oligometastatic Disease of the Abdomen and Central Thorax: Characterization of Potential Advantages","volume":"96","author":"Henke","year":"2016","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"196","DOI":"10.1016\/j.semradonc.2014.02.008","article-title":"The ViewRay system: Magnetic resonance\u2013guided and controlled radiotherapy","volume":"24","author":"Mutic","year":"2014","journal-title":"Semin. Radiat. Oncol."},{"key":"ref_19","first-page":"98","article-title":"Technical design and concept of a 0.35 T MR-linac","volume":"18","year":"2019","journal-title":"Clin. Transl. Radiat. Oncol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"N229","DOI":"10.1088\/0031-9155\/54\/12\/N01","article-title":"Integrating a 1.5 T MRI scanner with a 6 MV accelerator: Proof of concept","volume":"54","author":"Raaymakers","year":"2009","journal-title":"Phys. Med. Biol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"L41","DOI":"10.1088\/1361-6560\/aa9517","article-title":"First patients treated with a 1.5 T MRI-Linac: Clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment","volume":"62","author":"Raaymakers","year":"2017","journal-title":"Phys. Med. Biol."},{"key":"ref_22","first-page":"77","article-title":"Making on-Line Adaptive Radiotherapy Possible Using Artificial Intelligence and Machine Learning for Efficient Daily Re-Planning","volume":"8","author":"Archambault","year":"2020","journal-title":"Med. Phys. Int."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"R349","DOI":"10.1088\/0031-9155\/59\/21\/R349","article-title":"MR guidance in radiotherapy","volume":"59","author":"Lagendijk","year":"2014","journal-title":"Phys. Med. Biol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"20160667","DOI":"10.1259\/bjr.20160667","article-title":"The future of image-guided radiotherapy will be MR guided","volume":"90","author":"Pollard","year":"2017","journal-title":"Br. J. Radiol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.phro.2021.07.002","article-title":"The impact of image acquisition time on registration, delineation and image quality for magnetic resonance guided radiotherapy of prostate cancer patients","volume":"19","author":"Nowee","year":"2021","journal-title":"Phys. Imaging Radiat. Oncol."},{"key":"ref_26","first-page":"140","article-title":"The clinical introduction of MR-guided radiation therapy from a RTT perspective","volume":"18","author":"Botman","year":"2019","journal-title":"Clin. Transl. Radiat. Oncol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"160","DOI":"10.1177\/0146645318764092","article-title":"The need for, and implementation of, image guidance in radiation therapy","volume":"47","author":"Ibbott","year":"2018","journal-title":"Ann. ICRP"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1016\/j.tipsro.2022.08.004","article-title":"Online adaptive MR-guided radiotherapy: Conformity of contour adaptation for prostate cancer, rectal cancer and lymph node oligometastases among radiation therapists and radiation oncologists","volume":"23","author":"Rasing","year":"2022","journal-title":"Tech. Innov. Patient Support Radiat. Oncol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"100239","DOI":"10.1016\/j.tipsro.2024.100239","article-title":"Evaluation of clinical parallel workflow in online adaptive MR-guided Radiotherapy: A detailed assessment of treatment session times","volume":"29","author":"Votta","year":"2024","journal-title":"Tech. Innov. Patient Support Radiat. Oncol."},{"key":"ref_30","unstructured":"Varian Medical Systems (2021). Ethos Algorithms Reference Guide, Varian Medical Systems, Inc."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1022","DOI":"10.1016\/j.ijrobp.2022.06.078","article-title":"In Silico Trial of Computed Tomography-Guided Stereotactic Adaptive Radiation Therapy (CT-STAR) for the Treatment of Abdominal Oligometastases","volume":"114","author":"Schiff","year":"2022","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1186\/s13014-022-02125-z","article-title":"The first reported case of a patient with pancreatic cancer treated with cone beam computed tomography-guided stereotactic adaptive radiotherapy (CT-STAR)","volume":"17","author":"Kim","year":"2022","journal-title":"Radiat. Oncol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"e13827","DOI":"10.1002\/acm2.13827","article-title":"Potential utility of cone-beam CT-guided adaptive radiotherapy under end-exhalation breath-hold conditions for pancreatic cancer","volume":"24","author":"Ogawa","year":"2023","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2472","DOI":"10.1002\/mp.14121","article-title":"CBCT-based synthetic CT generation using deep-attention cycleGAN for pancreatic adaptive radiotherapy","volume":"47","author":"Liu","year":"2020","journal-title":"Med. Phys."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"012079","DOI":"10.1088\/1742-6596\/489\/1\/012079","article-title":"The Reconstruction Toolkit (RTK), an open-source cone-beam CT reconstruction toolkit based on the Insight Toolkit (ITK)","volume":"489","author":"Rit","year":"2014","journal-title":"J. Phys. Conf. Ser."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1109\/TMI.1982.4307572","article-title":"An Improved Algorithm for Reprojecting Rays through Pixel Images","volume":"1","author":"Joseph","year":"1982","journal-title":"IEEE Trans. Med. Imaging"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"K\u00f6nig, L., and R\u00fchaak, J. (May, January 29). A fast and accurate parallel algorithm for non-linear image registration using normalized gradient fields. Proceedings of the 2014 IEEE 11th International Symposium on Biomedical Imaging (ISBI), Beijing, China.","DOI":"10.1109\/ISBI.2014.6867937"},{"key":"ref_38","first-page":"255","article-title":"Highly accurate fast lung CT registration","volume":"8669","author":"Heldmann","year":"2013","journal-title":"Proc. SPIE Med. Imaging"},{"key":"ref_39","first-page":"702","article-title":"Diffeomorphic Registration Using B-Splines","volume":"Volume 4191","author":"Larsen","year":"2006","journal-title":"Medical Image Computing and Computer-Assisted Intervention\u2014MICCAI 2006"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Smolders, A., Choulilitsa, E., Czerska, K., Bizzocchi, N., Krcek, R., Lomax, A., Weber, D.C., and Albertini, F. (2023). Dosimetric comparison of autocontouring techniques for online adaptive proton therapy. Phys. Med. Biol., 68.","DOI":"10.1088\/1361-6560\/ace307"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Nenoff, L., Amstutz, F., Murr, M., Archibald-Heeren, B., Fusella, M., Hussein, M., Lechner, W., Zhang, Y., Sharp, G., and Osorio, E.V. (2023). Review and recommendations on deformable image registration uncertainties for radiotherapy applications. Phys. Med. Biol., 68.","DOI":"10.1088\/1361-6560\/ad0d8a"},{"key":"ref_42","first-page":"e9660","article-title":"Initial Evaluation of a Novel Cone-Beam CT-Based Semi-Automated Online Adaptive Radiotherapy System for Head and Neck Cancer Treatment\u2014A Timing and Automation Quality Study","volume":"12","author":"Yoon","year":"2020","journal-title":"Cureus"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"e13539","DOI":"10.1002\/acm2.13539","article-title":"Assessment of efficacy in automated plan generation for Varian Ethos intelligent optimization engine","volume":"23","author":"Pokharel","year":"2022","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"994","DOI":"10.1016\/j.ijrobp.2017.04.023","article-title":"Online Adaptive Radiation Therapy","volume":"99","author":"Keller","year":"2017","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."}],"container-title":["Current Oncology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1718-7729\/32\/2\/60\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,8]],"date-time":"2025-10-08T10:34:13Z","timestamp":1759919653000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1718-7729\/32\/2\/60"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,1,23]]},"references-count":44,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2025,2]]}},"alternative-id":["curroncol32020060"],"URL":"https:\/\/doi.org\/10.3390\/curroncol32020060","relation":{},"ISSN":["1718-7729"],"issn-type":[{"value":"1718-7729","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,1,23]]}}}