{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T02:59:03Z","timestamp":1784170743552,"version":"3.55.0"},"reference-count":13,"publisher":"Wiley","issue":"11","license":[{"start":{"date-parts":[[2023,6,24]],"date-time":"2023-06-24T00:00:00Z","timestamp":1687564800000},"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":[[2023,11]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>Magnetic resonance (MR)\u2010guided radiation therapy provides capabilities to utilize high\u2010resolution and real\u2010time MR imaging before and during treatment, which is critical for adaptive radiotherapy. This emerging modality has been promptly adopted in the clinic settings in advance of adaptations to reference dosimetry formalism that are needed to account for the presence of strong magnetic fields. In particular, the influence of magnetic field on the uncertainty of parameters in the reference dosimetry equation needs to be determined in order to fully characterize the uncertainty budget for reference dosimetry in MR\u2010guided radiation therapy systems.<\/jats:p><\/jats:sec><jats:sec><jats:title>Purpose<\/jats:title><jats:p>To identify and quantify key sources of uncertainty in the reference dosimetry of external high energy radiotherapy beams in the presence of a strong magnetic field.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>In the absence of a formalized Task Group report for reference dosimetry in MR\u2010integrated linacs, the currently suggested formalism follows the TG\u201051 protocol with the addition of a quality conversion factor <jats:italic>k<jats:sub>BQ<\/jats:sub><\/jats:italic> accounting for the effects of the magnetic field on ionization chamber response. In this work, we quantify various sources of uncertainty that impact each of the parameters in the formalism, and evaluate their overall contribution to the final dose. Measurements are done in a 1.5\u00a0T MR\u2010Linac (Unity, Elekta AB, Stockholm, Sweden) which integrates a 1.5\u00a0T Philips MR scanner and a 7\u00a0MVFFF linac. The responses of several reference\u2010class small volume ionization chambers (Exradin:A1SL, IBA:CC13, PTW:Semiflex\u20103D) and Farmer type ionization chambers (Exradin:A19, IBA:FC65\u2010G) were evaluated throughout this process. Long\u2010term reproducibility and stability of beam quality, , was also measured with an in\u2010house built phantom.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Relative to the conventional external high energy linacs, the uncertainty on overall reference dose in MR\u2010linac is more significantly affected by the chamber setup: A translational displacement along <jats:bold><jats:italic>y<\/jats:italic><\/jats:bold>\u2010axis of\u00a0\u00b1\u00a03\u00a0mm results in dose variation of\u00a0&lt;\u00a0|0.20|\u00a0\u00b1\u00a00.02% (k\u00a0=\u00a01), while rotation of\u00a0\u00b1\u00a05\u00b0 in horizontal and vertical parallel planes relative to relative to the direction of magnetic field, did not exceed variation of\u00a0&lt;\u00a0|0.44|\u00a0\u00b1\u00a00.02% for all 5 ionization chambers. We measured a larger dose variation for <jats:bold><jats:italic>xy<\/jats:italic><\/jats:bold>\u2010plane (horizontal) rotations (&lt;\u00a0|0.44|\u00a0\u00b1\u00a00.02% (k\u00a0=\u00a01)) than for <jats:bold><jats:italic>yz<\/jats:italic><\/jats:bold>\u2010plane (vertical) rotations (&lt;\u00a0||0.28|\u00a0\u00b1\u00a00.02% (k\u00a0=\u00a01)), which we associate with the gradient of <jats:italic>k<jats:sub>B,Q<\/jats:sub><\/jats:italic> as a function of chamber orientation with respect to direction of the B<jats:sub>0<\/jats:sub>\u2010field. Uncertainty in <jats:italic>P<\/jats:italic><jats:sub>ion<\/jats:sub> (for two depths), <jats:italic>P<\/jats:italic><jats:sub>pol<\/jats:sub> (with various sub\u2010studies including effects of cable length, cable looping in the MRgRT bore, connector type in magnetic environment), and <jats:italic>P<\/jats:italic><jats:sub>rp<\/jats:sub> were determined. Combined conversion factor <jats:italic>k<\/jats:italic><jats:sub>Q<\/jats:sub>\u00d7 <jats:italic>k<jats:sub>B,Q<\/jats:sub><\/jats:italic> was provided for two reference depths at four cardinal angle orientations. Over a two\u2010year period, beam quality was quite stable with  being 0.669\u00a0\u00b1\u00a00.01%. The actual magnitude of  was measured using identical equipment and compared between two different Elekta Unity MR\u2010Linacs with results agreeing to within 0.21%.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>In this work, the uncertainty of a number of parameters influencing reference dosimetry was quantified. The results of this work can be used to identify best practice guidelines for reference dosimetry in the presence of magnetic fields, and to evaluate an uncertainty budget for future reference dosimetry protocols for MR\u2010linac.<\/jats:p><\/jats:sec>","DOI":"10.1002\/acm2.14087","type":"journal-article","created":{"date-parts":[[2023,6,25]],"date-time":"2023-06-25T01:47:41Z","timestamp":1687657661000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Quantifying uncertainties associated with reference dosimetry in an MR\u2010Linac"],"prefix":"10.1002","volume":"24","author":[{"given":"Viktor","family":"Iakovenko","sequence":"first","affiliation":[{"name":"Division of Medical Physics and Engineering Department of Radiation Oncology University of Texas Southwestern Medical Center Dallas Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brian","family":"Keller","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology Sunnybrook Health Sciences Centre University of Toronto Toronto Ontario Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Victor N.","family":"Malkov","sequence":"additional","affiliation":[{"name":"Mayo Clinic Rochester Minnesota USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Arjun","family":"Sahgal","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology Sunnybrook Health Sciences Centre University of Toronto Toronto Ontario Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Arman","family":"Sarfehnia","sequence":"additional","affiliation":[{"name":"Department of Radiation Oncology Sunnybrook Health Sciences Centre University of Toronto Toronto Ontario Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2023,6,24]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"publisher","DOI":"10.1186\/s13014-019-1308-y"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1186\/s13014-020-01524-4"},{"key":"e_1_2_9_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijrobp.2017.11.009"},{"key":"e_1_2_9_5_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.598691"},{"key":"e_1_2_9_6_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4866223"},{"key":"e_1_2_9_7_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4959785"},{"key":"e_1_2_9_8_1","doi-asserted-by":"publisher","DOI":"10.1002\/mp.12716"},{"key":"e_1_2_9_9_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361\u20106560\/ab9efe"},{"key":"e_1_2_9_10_1","doi-asserted-by":"publisher","DOI":"10.1002\/mp.14025"},{"key":"e_1_2_9_11_1","unstructured":"Technical publication. Elekta Unit. Device Acceptance Tests. Document ID: 1536467 02.2018. p.129."},{"key":"e_1_2_9_12_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.1573205"},{"key":"e_1_2_9_13_1","doi-asserted-by":"publisher","DOI":"10.1088\/1361-6560\/ab807b"},{"key":"e_1_2_9_14_1","doi-asserted-by":"publisher","DOI":"10.1002\/mp.14468"}],"container-title":["Journal of Applied Clinical Medical Physics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/aapm.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/acm2.14087","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,11,15]],"date-time":"2023-11-15T21:29:59Z","timestamp":1700083799000},"score":1,"resource":{"primary":{"URL":"https:\/\/aapm.onlinelibrary.wiley.com\/doi\/10.1002\/acm2.14087"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,6,24]]},"references-count":13,"journal-issue":{"issue":"11","published-print":{"date-parts":[[2023,11]]}},"alternative-id":["10.1002\/acm2.14087"],"URL":"https:\/\/doi.org\/10.1002\/acm2.14087","archive":["Portico"],"relation":{},"ISSN":["1526-9914","1526-9914"],"issn-type":[{"value":"1526-9914","type":"print"},{"value":"1526-9914","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,6,24]]},"assertion":[{"value":"2023-03-02","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2023-05-23","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2023-06-24","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e14087"}}