{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T17:49:34Z","timestamp":1791395374744,"version":"4.3.3"},"reference-count":26,"publisher":"Wiley","issue":"11","license":[{"start":{"date-parts":[[2023,5,10]],"date-time":"2023-05-10T00:00:00Z","timestamp":1683676800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/100014132","name":"European Metrology Programme for Innovation and Research","doi-asserted-by":"publisher","award":["19NRM01 MRgRT\u2010DOS"],"award-info":[{"award-number":["19NRM01 MRgRT\u2010DOS"]}],"id":[{"id":"10.13039\/100014132","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["aapm.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2023,11]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>As it promises more precise and conformal radiation treatments, magnetic resonance imaging\u2010integrated proton therapy (MRiPT) is seen as a next step in image guidance for proton therapy. The Lorentz force, which affects the course of the proton pencil beams, presents a problem for beam delivery in the presence of a magnetic\u00a0field.<\/jats:p><\/jats:sec><jats:sec><jats:title>Purpose<\/jats:title><jats:p>To investigate the influence of the 0.32\u2010T perpendicular magnetic field of an MR scanner on the delivery of proton pencil beams inside an MRiPT prototype\u00a0system.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>An MRiPT prototype comprising of a horizontal pencil beam scanning beam line and an open 0.32\u2010T MR scanner was used to evaluate the impact of the vertical magnetic field on proton beam deflection and dose spot pattern deformation. Three different proton energies (100, 150, and 220 MeV) and two spot map sizes (15 \u00d7 15 and 30 \u00d7 20 cm<jats:sup>2<\/jats:sup>) at four locations along the beam path without and with magnetic field were measured. Pencil\u2010beam dose spots were measured using EBT3 films and a 2D scintillation detector. To study the magnetic field effects, a 2D Gaussian fit was applied to each individual dose spot to determine the central position , minimum and maximum lateral standard deviation ( and ), orientation (\u03b8), and the eccentricity (\u03b5).<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The dose spots were subjected to three simultaneous effects: (a) lateral horizontal beam deflection, (b) asymmetric trapezoidal deformation of the dose spot pattern, and (c) deformation and rotation of individual dose spots. The strongest effects were observed at a proton energy of 100 MeV with a horizontal beam deflection of 14\u2013186 mm along the beam path. Within the central imaging field of the MR scanner, the maximum relative dose spot size  decreased by up to 3.66%, while  increased by a maximum of 2.15%. The largest decrease and increase in the eccentricity of the dose spots were 0.08 and 0.02, respectively. The spot orientation \u03b8 was rotated by a maximum of 5.39\u00b0. At the higher proton energies, the same effects were still seen, although to a lesser\u00a0degree.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>The effect of an MRiPT prototype's magnetic field on the proton beam path, dose spot pattern, and dose spot form has been measured for the first time. The findings show that the impact of the MF must be appropriately recognized in a future MRiPT treatment planning system. The results emphasize the need for additional research (e.g., effect of magnetic field on proton beams with range shifters and impact of MR imaging sequences) before MRiPT applications can be employed to treat patients.<\/jats:p><\/jats:sec>","DOI":"10.1002\/mp.16448","type":"journal-article","created":{"date-parts":[[2023,5,11]],"date-time":"2023-05-11T03:25:11Z","timestamp":1683775511000},"page":"7294-7303","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Technical note: Experimental dosimetric characterization of proton pencil beam distortion in a perpendicular magnetic field of an in\u2010beam MR scanner"],"prefix":"10.1002","volume":"50","author":[{"given":"Benjamin","family":"Gebauer","sequence":"first","affiliation":[{"name":"OncoRay\u2014National Center for Radiation Research in Oncology Faculty of Medicine and University Hospital Carl Gustav Carus Technische Universit\u00e4t Dresden, Helmholtz\u2010Zentrum 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Germany"},{"name":"Institute of Radiooncology\u2014OncoRay Helmholtz\u2010Zentrum Dresden\u2010Rossendorf Dresden Germany"},{"name":"Department of Radiotherapy and Radiation Oncology Faculty of Medicine and University Hospital Carl Gustav Carus Technische Universit\u00e4t Dresden Dresden Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Armin","family":"L\u00fchr","sequence":"additional","affiliation":[{"name":"Department of Physics TU Dortmund University Dortmund 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