{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T20:01:15Z","timestamp":1792785675752,"version":"4.5.0"},"reference-count":19,"publisher":"IOP Publishing","issue":"19","license":[{"start":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T00:00:00Z","timestamp":1790812800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T00:00:00Z","timestamp":1790812800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/iopscience.iop.org\/info\/page\/text-and-data-mining"}],"funder":[{"name":"Princess Margaret Cancer Foundation","award":["IAF"],"award-info":[{"award-number":["IAF"]}],"id":[{"id":"https:\/\/ror.org\/00ctsa544","id-type":"ROR","asserted-by":"crossref"}]}],"content-domain":{"domain":["iopscience.iop.org"],"crossmark-restriction":false},"short-container-title":["Phys. Med. Biol."],"published-print":{"date-parts":[[2026,10,14]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    <jats:italic>Objective.<\/jats:italic>\n                    Integrating medical linear accelerators and magnetic resonance imaging (MRI) scanners for MRI-guided radiotherapy (MRgRT) is complicated by mutual magnetic field coupling, making efficient field mapping crucial. This study proposes a computationally efficient methodology to characterize an MR scanner\u2019s magnetic fringe field by solving a boundary value problem (BVP) from sparsely sampled data. This approach accurately maps fields in free space and near ferromagnetic materials without requiring proprietary internal MR coil models or full-scale room simulations.\n                    <jats:italic>Approach.<\/jats:italic>\n                    A full-scale finite element method (FEM) model of a proximity-type MRgRT system, validated against experimental measurements, was used as the reference. A hybrid BVP methodology was developed where Laplace\u2019s equation was first solved using sparsely sampled magnetic field boundary conditions. To account for the linac, this free-space solution was subsequently used as an initial condition for a refined model that incorporated the ferromagnetic properties of the linac head and was solved using Maxwell\u2019s equations. Accuracy was assessed by comparing the BVP solutions to the full-scale FEM reference across various sampling resolutions.\n                    <jats:italic>Main results.<\/jats:italic>\n                    The BVP approach reconstructed the magnetic field to within 1 G of the reference using a coarse 40 cm boundary sampling. The hybrid method successfully characterized field distortions from the linac; ignoring the ferromagnetic structure led to errors of \u22127 G to 2 G near the component, whereas including it reduced the discrepancy to within 1 G. The methodology was efficient, reducing computation time from 2 h for the full-scale model to under 10 min, while using a fraction of the memory.\n                    <jats:italic>Significance.<\/jats:italic>\n                    This study presents a validated, efficient, and accessible BVP-based methodology for magnetic field characterization in MRgRT systems. By enabling accurate field mapping from sparse data, accounting for ferromagnetic components, and drastically reducing computational demands, this approach offers a robust tool for rapid engineering assessments and serves as a practical alternative to complex full-scale simulations.\n                  <\/jats:p>","DOI":"10.1088\/1361-6560\/aeabe6","type":"journal-article","created":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T22:53:29Z","timestamp":1790204009000},"page":"195017","update-policy":"https:\/\/doi.org\/10.1088\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Characterizing magnetic field coupling in MRI-guided radiotherapy by solving a dirichlet problem with sparsely sampled boundary conditions"],"prefix":"10.1088","volume":"71","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-2946-5903","authenticated-orcid":true,"given":"K","family":"Vat","sequence":"first","affiliation":[{"name":"UMC Utrecht"},{"name":"Eindhoven University of Technology"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2314-7884","authenticated-orcid":true,"given":"T","family":"Stanescu","sequence":"additional","affiliation":[{"name":"University Health Network"},{"name":"University of Toronto"},{"name":"University of Toronto"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"266","published-online":{"date-parts":[[2026,10,1]]},"reference":[{"key":"pmbaeabe6bib1","article-title":"Combined radiation therapy and magnetic resonance unit. 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