{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T18:23:43Z","timestamp":1784744623064,"version":"3.55.0"},"reference-count":25,"publisher":"Public Library of Science (PLoS)","issue":"7","license":[{"start":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T00:00:00Z","timestamp":1784678400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100014188","name":"Ministry of Science and ICT, South Korea","doi-asserted-by":"publisher","award":["2017R1C1B1006636"],"award-info":[{"award-number":["2017R1C1B1006636"]}],"id":[{"id":"10.13039\/501100014188","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100014188","name":"Ministry of Science and ICT, South Korea","doi-asserted-by":"publisher","award":["RS-2025-00339804"],"award-info":[{"award-number":["RS-2025-00339804"]}],"id":[{"id":"10.13039\/501100014188","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Hypofractionated external beam radiotherapy for prostate cancer necessitates precise rectal dose evaluation. We fabricated a radiochromic polyurethane-based in vivo rectal dosimeter with a custom MRI marker and a patient-specific applicator for in vivo dose verification (IDV) during gated MR-image guided radiotherapy (MR-IGRT).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>The dosimeter featured a radiochromic polyurethane active layer, incorporating leucomalachite green (LMG) and tartrazine. To accommodate anatomical variations, a detachable PMMA applicator was designed in five sizes. For localization, four elastomeric materials, including two polyurethane-based and two silicone-based materials, were evaluated as candidate MRI markers. Post-irradiation fading was assessed over time to evaluate measurement stability. A dose-response calibration was performed to establish a linear relationship between net optical density (OD) and absorbed dose. Furthermore, dose uncertainty was analyzed based on the law of error propagation. For verification, in vivo measurements were conducted for two patients and compared with TPS-calculated doses.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Vyta Flex 20 was selected as the optimal MRI marker due to its high signal intensity and ease of fabrication. Post-irradiation net OD showed a dose-dependent temporal response, and the readout time was standardized to 2 h. The dosimeter\u2019s sensitivity was 0.00253 cGy\n                      <jats:sup>-1<\/jats:sup>\n                      . Dose uncertainties were determined to be 2.1%, 2.0%, and 1.6% at 100, 200, and 300 cGy, respectively. In vivo verification showed mean dose differences of 3.7\u2009\u00b1\u20091.4% (95% CI, 0.1\u20137.3%) for patient #1 and 5.9\u2009\u00b1\u20092.1% (95% CI, 0.8\u201311.1%) for patient #2. Measured doses were consistently higher than TPS-calculated doses, suggesting possible contributions from localization uncertainty in high-dose-gradient regions and the material-dependent response of the radiochromic active layer.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>The fabricated radiochromic dosimeter with a custom MRI marker and adjustable applicator demonstrated preliminary feasibility as a proof-of-concept system for in vivo rectal dose verification during MR-IGRT. Further studies with larger patient cohorts and more treatment fractions are required to validate its reproducibility, statistical robustness, and clinical utility. Further refinement in positioning is also needed, particularly in dose-gradient regions.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pone.0354149","type":"journal-article","created":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T17:28:42Z","timestamp":1784741322000},"page":"e0354149","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["In vivo rectal dosimeter with MRI marker"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2155-3793","authenticated-orcid":true,"given":"Euntaek","family":"Yoon","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1914-8163","authenticated-orcid":true,"given":"Jin Dong","family":"Cho","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chang Heon","family":"Choi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jin Ho","family":"Kim","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7075-8293","authenticated-orcid":true,"given":"Jeong Ho","family":"Kim","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3617-3870","authenticated-orcid":true,"given":"Jong Min","family":"Park","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jung-in","family":"Kim","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2026,7,22]]},"reference":[{"issue":"6","key":"pone.0354149.ref001","article-title":"External beam radiation therapy for prostate cancer","volume":"50","author":"EM Horwitz","year":"2000","journal-title":"CA Cancer J Clin"},{"key":"pone.0354149.ref002","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1016\/j.radonc.2019.08.027","article-title":"ESTRO ACROP consensus guideline on the use of image guided radiation therapy for localized prostate cancer","volume":"141","author":"P Ghadjar","year":"2019","journal-title":"Radiother Oncol"},{"issue":"1067","key":"pone.0354149.ref003","doi-asserted-by":"crossref","first-page":"20160312","DOI":"10.1259\/bjr.20160312","article-title":"Target margins in radiotherapy of prostate cancer","volume":"89","author":"S Yartsev","year":"2016","journal-title":"Br J Radiol"},{"issue":"3","key":"pone.0354149.ref004","doi-asserted-by":"crossref","first-page":"936","DOI":"10.1016\/j.ijrobp.2007.06.063","article-title":"Prostate planning treatment volume margin calculation based on the ExacTrac X-Ray 6D image-guided system: margins for various clinical implementations","volume":"69","author":"S Alonso-Arrizabalaga","year":"2007","journal-title":"Int J Radiat Oncol Biol Phys"},{"issue":"2","key":"pone.0354149.ref005","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1016\/S1470-2045(20)30581-7","article-title":"Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer (HYPO-RT-PC): patient-reported quality-of-life outcomes of a randomised, controlled, non-inferiority, phase 3 trial","volume":"22","author":"P Fransson","year":"2021","journal-title":"Lancet Oncol"},{"issue":"3","key":"pone.0354149.ref006","doi-asserted-by":"crossref","first-page":"811","DOI":"10.1016\/j.ijrobp.2009.05.054","article-title":"Single-fraction high-dose-rate brachytherapy and hypofractionated external beam radiotherapy for men with intermediate-risk prostate cancer: analysis of short- and medium-term toxicity and quality of life","volume":"77","author":"GC Morton","year":"2010","journal-title":"Int J Radiat Oncol Biol Phys"},{"issue":"2","key":"pone.0354149.ref007","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1016\/j.semradonc.2009.11.007","article-title":"Adaptive radiation therapy for prostate cancer","volume":"20","author":"M Ghilezan","year":"2010","journal-title":"Semin Radiat Oncol"},{"issue":"12","key":"pone.0354149.ref008","doi-asserted-by":"crossref","first-page":"6199","DOI":"10.1118\/1.3512791","article-title":"Monte Carlo calculation of imaging doses from diagnostic multidetector CT and kilovoltage cone-beam CT as part of prostate cancer treatment plans","volume":"37","author":"A Ding","year":"2010","journal-title":"Med Phys"},{"issue":"3","key":"pone.0354149.ref009","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.radonc.2016.04.014","article-title":"MRI-guided prostate adaptive radiotherapy - 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