{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,12]],"date-time":"2026-01-12T10:33:40Z","timestamp":1768214020860,"version":"3.49.0"},"reference-count":44,"publisher":"Wiley","issue":"12","license":[{"start":{"date-parts":[[2025,12,4]],"date-time":"2025-12-04T00:00:00Z","timestamp":1764806400000},"content-version":"vor","delay-in-days":3,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"},{"start":{"date-parts":[[2025,12,1]],"date-time":"2025-12-01T00:00:00Z","timestamp":1764547200000},"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":[[2025,12]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Skin dose measurements for the inline MRI\u2010linac show a highly concentrated skin dose hot spot at the central axis of the beam. This is because the electron contamination is focused in the presence of the inline magnetic field, causing a significant entry surface (or skin) dose hot spot. The future clinical treatment will employ a 2 cm water electron filter to reduce electron contamination from the X\u2010ray beam; however, this approach affects the overall dose distribution, and the skin dose remains significantly high.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose<\/jats:title>\n                    <jats:p>To evaluate and compare the effectiveness of a copper electron filter (CuEF) and a water electron filter (WEF) in reducing the skin dose on the inline MRI\u2010linac, using Monte Carlo simulations and experimental\u00a0measurements.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      The magnetic field maps, designed using a 3D magnetic field model for a 1 T MRI\u2010linac in COMSOL Multiphysics, were subsequently integrated into the Geant4 Monte Carlo model of the Australian MRI\u2010linac. The Geant4 geometry also included the WEF, CuEF and a 30\u00a030\u00a030 cm\n                      <jats:sup>3<\/jats:sup>\n                      water phantom. Simulations were performed for field sizes 2.4\u00a02.4 cm\n                      <jats:sup>2<\/jats:sup>\n                      , 7.2\u00a07.2 cm\n                      <jats:sup>2<\/jats:sup>\n                      and 12.4\u00a012.4 cm\n                      <jats:sup>2<\/jats:sup>\n                      . To compare the efficiency of a 2 cm water block in mitigating the electron contamination, simulations were performed with WEF positioned above the phantom surface. Central axis percentage depth dose and surface skin dose values at 70  depth were measured using high\u2010resolution scoring voxels. Additional simulations were performed by placing CuEF at varying distances from the MRI isocenter. The simulation results were further validated by the experimental measurements performed using the MO\n                      <jats:italic>Skin<\/jats:italic>\n                      \u2122 detector by incorporating the physical prototypes of the CuEF and WEF in the pre\u2010clinical setup of\u00a0MRI\u2010linac.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      In the presence of a magnetic field, the skin dose values were measured to be 122.5% (2.4\u00a02.4 cm\n                      <jats:sup>2<\/jats:sup>\n                      ), 194.8% (7.2\u00a07.2 cm\n                      <jats:sup>2<\/jats:sup>\n                      ), and 260.4% (12.4\u00a012.4 cm\n                      <jats:sup>2<\/jats:sup>\n                      ) of the dose at\n                      <jats:italic>d<\/jats:italic>\n                      <jats:sub>max<\/jats:sub>\n                      (1.5 cm depth) for near 0 T measurements. Adding the WEF 30 cm above the phantom surface reduces these skin dose values; however, the hot spot's intensity remains substantial, and the skin dose is higher than\n                      <jats:italic>\n                        d\n                        <jats:sub>max<\/jats:sub>\n                      <\/jats:italic>\n                      . The CuEF was found to be more effective in reducing the skin dose hot spots across all three field sizes. Positioning the CuEF 10 cm above the phantom surface reduced the skin dose values by about 25%, 53%, and 64% for the field size 2.4\u00a02.4 cm\n                      <jats:sup>2<\/jats:sup>\n                      , 7.2\u00a07.2 cm\n                      <jats:sup>2<\/jats:sup>\n                      , and 12.4\u00a012.4 cm\n                      <jats:sup>2<\/jats:sup>\n                      ,\u00a0respectively.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Incorporating the CuEF above the phantom surface in the inline MRI\u2010linac prototype notably reduces the intensity of the skin dose hot spot, proving to be a more effective solution than a standard 2 cm water block across all field\u00a0sizes.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/mp.70166","type":"journal-article","created":{"date-parts":[[2025,12,5]],"date-time":"2025-12-05T03:56:55Z","timestamp":1764907015000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Investigating the use of a solid water and copper electron filter for reducing skin dose in an inline MRI\u2010linac"],"prefix":"10.1002","volume":"52","author":[{"given":"Madiha","family":"Tai","sequence":"first","affiliation":[{"name":"Centre for Medical Radiation Physics University of Wollongong Wollongong NSW Australia"},{"name":"GenesisCare, St Vincent's Hospital Darlinghurst NSW Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jarrad","family":"Begg","sequence":"additional","affiliation":[{"name":"Department of Medical Physics Liverpool and Macarthur Cancer Therapy Centre Liverpool NSW Australia"},{"name":"Ingham Institute for Applied Medical Research Liverpool NSW 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