{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,2]],"date-time":"2026-11-02T15:27:15Z","timestamp":1793633235546,"version":"4.5.1"},"reference-count":34,"publisher":"Wiley","issue":"8","license":[{"start":{"date-parts":[[2025,9,3]],"date-time":"2025-09-03T00:00:00Z","timestamp":1756857600000},"content-version":"vor","delay-in-days":33,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"},{"start":{"date-parts":[[2025,8,1]],"date-time":"2025-08-01T00:00:00Z","timestamp":1754006400000},"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":[[2025,8]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Low\u2010field MRI provides superior soft\u2010tissue contrast compared to CT while costing significantly less than high\u2010field MRI, which makes it a more accessible option for MRI\u2010guided radiation therapy planning. Four\u2010dimensional MRI (4D\u2010MRI) is a technique that has been increasingly adopted clinically for internal target volume (ITV) delineation in free\u2010breathing liver radiotherapy planning, and it requires high spatial resolution and accurate respiratory phase differentiation to enable precise dose planning. The feasibility of 4D\u2010MRI at low\u2010field strength, specifically at 0.55T, has not been evaluated.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose<\/jats:title>\n                    <jats:p>This study aims to investigate the feasibility of 4D\u2010MRI for ITV delineation in liver radiation therapy planning using a commercial 0.55T MRI scanner.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>A 3D stack\u2010of\u2010stars T1\u2010weighted sequence was implemented with two respiratory self\u2010navigation methods: (1) k\u2010space center point tracking (\u201ck\u2010center\u201d) and (2) superior\u2010inferior one\u2010dimensional projection\u2010based tracking (\u201cSI\u2010projection\u201d). These methods were evaluated using ten phantom scans simulating diverse respiratory motion patterns and five liver tumor patient scans.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Both self\u2010navigation approaches demonstrated strong correlation between the extracted self\u2010gating signals (SGS) and ground\u2010truth motion traces across four breathing patterns: sinusoidal waveform, typical respiration, drifting motion, and irregular breathing. For sinusoidal motion, measured ITV deviations were within 1.1% of the true ITV for both methods. In non\u2010sinusoidal cases, ITV deviations remained within 2% except for two drifting motion cases where k\u2010center SGS based reconstructions showed deviations of 6.0% and 2.4%. In liver tumor patient scans, both self\u2010navigation techniques produced images with sufficient tumor delineation for treatment planning, with SI\u2010projection SGS\u2010based reconstructions yielding sharper images than k\u2010center SGS\u2010based reconstructions. ITV volumes contoured by two radiation oncologists showed strong and comparable inter\u2010observer agreement across both techniques.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>This study demonstrates that 4D\u2010MRI at 0.55T is feasible and provides adequate image quality for ITV delineation. Self\u2010navigation techniques play an important role in improving the sharpness of tumor boundaries, with SI\u2010projection based self\u2010navigation offering superior performance in cases of irregular respiratory motion.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/mp.18069","type":"journal-article","created":{"date-parts":[[2025,9,4]],"date-time":"2025-09-04T05:39:21Z","timestamp":1756964361000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["4D\u2010MRI at 0.55T for internal target volume delineation in liver radiation therapy planning"],"prefix":"10.1002","volume":"52","author":[{"given":"Xin","family":"Miao","sequence":"first","affiliation":[{"name":"Department of Radiology Children's Hospital Los Angeles  Los Angeles California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pan","family":"Su","sequence":"additional","affiliation":[{"name":"Siemens Medical Solutions USA Inc.  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Malvern Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexandra E.","family":"Hotca","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology University of California San Francisco  San Francisco California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas A.","family":"Hope","sequence":"additional","affiliation":[{"name":"Department of Radiology and Biomedical Imaging University of California San Francisco  San Francisco California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cheng William","family":"Hong","sequence":"additional","affiliation":[{"name":"Department of Radiology and Biomedical Imaging University of California San Francisco  San Francisco California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emily K.","family":"Bergsland","sequence":"additional","affiliation":[{"name":"Department of Medicine University of California San Francisco  San Francisco California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mary","family":"Feng","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology University of California San Francisco  San Francisco California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jessica E.","family":"Scholey","sequence":"additional","affiliation":[{"name":"Department of Radiology and Biomedical Imaging University of California San Francisco  San Francisco California USA"},{"name":"Department of Radiation Oncology University of California San Francisco  San Francisco California USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2025,9,3]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijrobp.2012.12.014"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijrobp.2015.01.035"},{"key":"e_1_2_9_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.radonc.2018.05.006"},{"key":"e_1_2_9_5_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361\u20106560\/aae56d"},{"key":"e_1_2_9_6_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ctro.2020.05.002"},{"key":"e_1_2_9_7_1","doi-asserted-by":"publisher","DOI":"10.1002\/mrm.25753"},{"key":"e_1_2_9_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.radonc.2022.05.037"},{"key":"e_1_2_9_9_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4929552"},{"key":"e_1_2_9_10_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijrobp.2014.10.050"},{"key":"e_1_2_9_11_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361\u20106560\/aa54f2"},{"key":"e_1_2_9_12_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41598\u2010023\u201042773\u2010z"},{"key":"e_1_2_9_13_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361\u20106560\/abfada"},{"key":"e_1_2_9_14_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.phro.2018.09.004"},{"key":"e_1_2_9_15_1","doi-asserted-by":"publisher","DOI":"10.1148\/radiol.2019190452"},{"key":"e_1_2_9_16_1","doi-asserted-by":"publisher","DOI":"10.1002\/jmri.26637"},{"key":"e_1_2_9_17_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.radonc.2018.04.029"},{"key":"e_1_2_9_18_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361\u20106560\/abc937"},{"key":"e_1_2_9_19_1","doi-asserted-by":"publisher","DOI":"10.1002\/mp.16469"},{"key":"e_1_2_9_20_1","volume-title":"MAGNETOM Free.Max RT Edition Brochure","author":"Siemens Medical Solutions USA, Inc","year":"2024"},{"key":"e_1_2_9_21_1","doi-asserted-by":"publisher","DOI":"10.1109\/TMI.2006.885337"},{"key":"e_1_2_9_22_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhep.2012.01.031"},{"key":"e_1_2_9_23_1","unstructured":"GrimmR BlockKT HutterJ et\u00a0al.Self\u2010gating reconstructions of motion and perfusion for free\u2010breathing T1\u2010weighted DCEMRI of the thorax using 3 D stack\u2010of\u2010stars GRE imaging. 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