{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T07:51:11Z","timestamp":1792050671959,"version":"4.4.0"},"reference-count":34,"publisher":"IOP Publishing","issue":"20","license":[{"start":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T00:00:00Z","timestamp":1792022400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T00:00:00Z","timestamp":1792022400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/iopscience.iop.org\/info\/page\/text-and-data-mining"}],"content-domain":{"domain":["iopscience.iop.org"],"crossmark-restriction":false},"short-container-title":["Phys. Med. Biol."],"published-print":{"date-parts":[[2026,10,28]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    <jats:italic>Objective.<\/jats:italic>\n                    Synchrocyclotrons deliver radiation in distinct macro pulses with high instantaneous dose rate that distinguish them from isochronous cyclotrons and synchrotrons. The relatively high instantaneous dose rates associated with synchrocyclotrons require special consideration in measurement of the neutron dose. The objective of this work is to measure the out-of-field neutron ambient dose equivalent (H*(10)) as a conservative operational surrogate to assess the fetal dose due to secondary neutrons for a gantry-mounted synchrocyclotron proton therapy system when an intensity modulated proton therapy (IMPT) brain treatment is delivered with the dynamic aperture (DA), static aperture (SA), and no aperture (NA).\n                    <jats:italic>Approach.<\/jats:italic>\n                    A pencil beam scanning (PBS) gantry-mounted synchrocyclotron was used for beam delivery. IMPT plans employing the DA, SA, and NA, each with 3 fields (vertex, lateral, and posterior\u2013anterior (PA)) were optimized using the treatment planning system to treat a left-sided spherical brain target with 6 cm diameter to a total dose of 66 Gy (weighted by radiobiological effectiveness [RBE] 1.1) in 33 fractions. The plans were delivered to an anthropomorphic phantom and the neutron H*(10) was measured using two commercial rem-meters, a WENDI-II and a LUPIN-BF3-NP counter at 43, 53, 61, and 71 cm distance from the isocenter intended to mimic distances to a fetus at various gestational periods. To investigate the influence of the couch angle for the PA field, the neutron dose from the PA field was measured at several couch angles including 0\u00b0, 180\u00b0, and 270\u00b0.\n                    <jats:italic>Main results.<\/jats:italic>\n                    WENDI-II suffers from dead-time associated issues and underestimated the dose by a factor of \u223c1.7\u20132.7 compared to LUPIN-BF3-NP. H*(10) showed dependence on the measurement location and the use of field shaping system. The total H*(10) for 66 Gy-equivalent proton dose was estimated to be 10.7 mSv (9.7 mSv) and 4.9 mSv (4.5 mSv) at 43 and 71 cm distance from the isocenter, respectively, when the SA (DA) was used. Without an aperture the corresponding values were 11.8 mSv and 5.3 mSv. The 270\u00b0-couch-angle resulted in the highest neutron dose from the PA field by \u223c15% relative to the 0\u00b0-couch-angle, resulting in an increase in the neutron dose by \u223c5% for the whole treatment.\n                    <jats:italic>Significance.<\/jats:italic>\n                    WENDI-II is not a reliable device for in-room neutron dose measurement for synchrocyclotrons with high instantaneous dose rates. Employing appropriate use of the aperture system as well as avoiding the 270\u00b0 couch angle for the PA field can minimize the neutron dose in the gantry-mounted system studied in this work.\n                  <\/jats:p>","DOI":"10.1088\/1361-6560\/aeaf3e","type":"journal-article","created":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T07:06:52Z","timestamp":1792048012000},"page":"205001","update-policy":"https:\/\/doi.org\/10.1088\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Practical considerations in measuring out-of-field neutron dose for pulsed and gantry-mounted proton therapy machines"],"prefix":"10.1088","volume":"71","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-0630-1987","authenticated-orcid":true,"given":"Hailei","family":"Zhang","sequence":"first","affiliation":[{"name":"WashU Medicine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2604-5285","authenticated-orcid":true,"given":"Thomas R","family":"Mazur","sequence":"additional","affiliation":[{"name":"WashU Medicine"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5983-9837","authenticated-orcid":true,"given":"Gabriele","family":"Zorloni","sequence":"additional","affiliation":[{"name":"ELSE NUCLEAR s.r.l"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4148-0891","authenticated-orcid":true,"given":"Arash","family":"Darafsheh","sequence":"additional","affiliation":[{"name":"WashU Medicine"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"266","published-online":{"date-parts":[[2026,10,15]]},"reference":[{"key":"pmbaeaf3ebib1","doi-asserted-by":"publisher","first-page":"980","DOI":"10.1088\/1361-6498\/abaff4","type":"journal-article","article-title":"A Monte Carlo based analytic model of the in-room neutron ambient dose equivalent for a Mevion gantry-mounted passively scattered proton system","volume":"40","author":"Baradaran-Ghahfarokhi","year":"2020a","journal-title":"J. Radiol. Prot."},{"key":"pmbaeaf3ebib2","doi-asserted-by":"publisher","first-page":"4509","DOI":"10.1002\/mp.14299","type":"journal-article","article-title":"A Monte Carlo\u2010based analytic model of neutron dose equivalent for a Mevion gantry\u2010mounted passively scattered proton system for craniospinal irradiation","volume":"47","author":"Baradaran-Ghahfarokhi","year":"2020b","journal-title":"Med. Phys."},{"key":"pmbaeaf3ebib3","doi-asserted-by":"publisher","first-page":"15","DOI":"10.1016\/j.nima.2013.01.060","type":"journal-article","article-title":"LUPIN, a new instrument for pulsed neutron fields","volume":"712","author":"Caresana","year":"2013","journal-title":"Nucl. Instrum. Methods Phys. Res. A"},{"key":"pmbaeaf3ebib4","doi-asserted-by":"publisher","first-page":"203","DOI":"10.1016\/j.nima.2013.11.073","type":"journal-article","article-title":"Intercomparison of radiation protection instrumentation in a pulsed neutron field","volume":"737","author":"Caresana","year":"2014a","journal-title":"Nucl. Instrum. Methods Phys. Res. A"},{"key":"pmbaeaf3ebib5","doi-asserted-by":"publisher","first-page":"725","DOI":"10.15669\/pnst.4.725","type":"journal-article","article-title":"A neutron detector for pulsed mixed fields: preliminary measurements","volume":"4","author":"Caresana","year":"2014b","journal-title":"Prog. Nucl. Sci. Technol."},{"key":"pmbaeaf3ebib6","doi-asserted-by":"publisher","first-page":"1853","DOI":"10.1093\/rpd\/ncac215","type":"journal-article","article-title":"Measurements in pulsed neutron fields","volume":"199","author":"Caresana","year":"2023","journal-title":"Radiat. Prot. Dosim."},{"key":"pmbaeaf3ebib7","doi-asserted-by":"publisher","first-page":"67","DOI":"10.1093\/rpd\/nct312","type":"journal-article","article-title":"Instrument intercomparison in the high-energy mixed field at the CERN-EU reference field (CERF) facility","volume":"161","author":"Caresana","year":"2014c","journal-title":"Radiat. Prot. Dosim."},{"key":"pmbaeaf3ebib8","doi-asserted-by":"publisher","DOI":"10.1088\/1361-6560\/ae1ee5","type":"journal-article","article-title":"First multi-institutional systematic comparison of the neutron ambient dose equivalent produced by proton therapy systems","volume":"70","author":"Darafsheh","year":"2025","journal-title":"Phys. Med. Biol."},{"key":"pmbaeaf3ebib9","doi-asserted-by":"publisher","first-page":"24","DOI":"10.1016\/j.radmeas.2018.05.008","type":"journal-article","article-title":"Instrument intercomparison in the high-energy field at the CERN-EU reference field (CERF) facility and comparison with the 2017 FLUKA simulations","volume":"117","author":"Dinar","year":"2018","journal-title":"Radiat. Meas."},{"key":"pmbaeaf3ebib10","doi-asserted-by":"publisher","DOI":"10.1016\/j.adro.2024.101673","type":"journal-article","article-title":"Treatment of a pregnant patient with a brain tumor using pencil beam scanning proton therapy","volume":"10","author":"Dupere","year":"2025","journal-title":"Adv. Radiat. Oncol."},{"key":"pmbaeaf3ebib11","doi-asserted-by":"publisher","first-page":"853","DOI":"10.1016\/j.ijrobp.2023.09.040","type":"journal-article","article-title":"Pencil beam scanning proton therapy for pregnant patients with brain and head and neck cancers","volume":"118","author":"Dupere","year":"2024","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"pmbaeaf3ebib12","doi-asserted-by":"publisher","first-page":"683","DOI":"10.1088\/0031-9155\/61\/2\/683","type":"journal-article","article-title":"Dose assessment for the fetus considering scattered and secondary radiation from photon and proton therapy when treating a brain tumor of the mother","volume":"61","author":"Geng","year":"2016","journal-title":"Phys. Med. Biol."},{"key":"pmbaeaf3ebib13","doi-asserted-by":"publisher","DOI":"10.1259\/bjr.20190412","type":"journal-article","article-title":"Neutron dose and its measurement in proton therapy\u2014current State of Knowledge","volume":"93","author":"H\u00e4lg","year":"2020","journal-title":"Br. J. Radiol."},{"key":"pmbaeaf3ebib14","doi-asserted-by":"publisher","DOI":"10.1002\/acm2.13957","type":"journal-article","article-title":"Measurements of fetal dose with Mevion S250i proton therapy system with HYPERSCAN","volume":"24","author":"Hopfensperger","year":"2023","journal-title":"Appl. Clin. Med. Phys."},{"key":"pmbaeaf3ebib15","doi-asserted-by":"publisher","first-page":"pkag007","DOI":"10.1093\/jncics\/pkag007","type":"journal-article","article-title":"Pregnancy, cancer, and radiation-a modern refresher","volume":"10","author":"Kisling","year":"2026","journal-title":"JNCI Cancer Spectrum"},{"key":"pmbaeaf3ebib16","doi-asserted-by":"publisher","DOI":"10.1016\/j.radonc.2026.111600","type":"journal-article","article-title":"Radiation therapy and cancer during pregnancy\u2014current practice in the Netherlands","volume":"221","author":"Koken","year":"2026","journal-title":"Radiother. Oncol."},{"key":"pmbaeaf3ebib17","doi-asserted-by":"publisher","first-page":"306","DOI":"10.1016\/j.ijrobp.2023.12.039","type":"journal-article","article-title":"In Regard to Dupere et al. international","volume":"119","author":"Lin","year":"2024","journal-title":"Int. J. Radiat. Oncol. Biol. Phys."},{"key":"pmbaeaf3ebib18","doi-asserted-by":"publisher","first-page":"591","DOI":"10.1097\/GRF.0b013e318236e935","type":"journal-article","article-title":"Review of radiation therapy in the pregnant cancer patient","volume":"54","author":"Martin","year":"2011","journal-title":"Clin. Obstet. Gynecol."},{"key":"pmbaeaf3ebib19","doi-asserted-by":"publisher","DOI":"10.1016\/j.radphyschem.2024.112362","type":"journal-article","article-title":"Neutron detectors in proton therapy: calibration, operational in situ verification, and comparison with Monte Carlo simulation","volume":"228","author":"Mart\u00ednez-Franc\u00e9s","year":"2025","journal-title":"Radiat. Phys. Chem."},{"key":"pmbaeaf3ebib20","doi-asserted-by":"publisher","DOI":"10.1088\/1361-6560\/ae72e7","type":"journal-article","article-title":"Out-of-field neutron doses in proton therapy: from experimental characterization to a practical calculation tool","volume":"71","author":"Mart\u00ednez-Franc\u00e9s","year":"2026","journal-title":"Phys. Med. Biol."},{"key":"pmbaeaf3ebib21","author":"National Research Council of the National Academies","year":"2006","type":"book"},{"key":"pmbaeaf3ebib22","doi-asserted-by":"publisher","first-page":"R155","DOI":"10.1088\/0031-9155\/60\/8\/R155","type":"journal-article","article-title":"The physics of proton therapy","volume":"60","author":"Newhauser","year":"2015","journal-title":"Phys. Med. Biol."},{"key":"pmbaeaf3ebib23","doi-asserted-by":"publisher","first-page":"170","DOI":"10.1097\/00004032-200008000-00010","type":"journal-article","article-title":"WENDI: an improved neutron rem meter","volume":"79","author":"Olsher","year":"2000","journal-title":"Health Phys."},{"key":"pmbaeaf3ebib24","author":"Paganetti","year":"2025","edition":"3rd edn","type":"book"},{"key":"pmbaeaf3ebib25","doi-asserted-by":"publisher","DOI":"10.1002\/acm2.14394","type":"journal-article","article-title":"Fetal dose assessment in a pregnant patient with brain tumor: a comparative study of proton PBS and 3DCRT\/VMAT radiation therapy techniques","volume":"25","author":"Rahimi","year":"2024","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"pmbaeaf3ebib26","doi-asserted-by":"publisher","first-page":"5099","DOI":"10.1002\/mp.16897","type":"journal-article","article-title":"Range shifter contribution to neutron exposure of patients undergoing proton pencil beam scanning","volume":"51","author":"Romero-Exp\u00f3sito","year":"2024","journal-title":"Med. Phys."},{"key":"pmbaeaf3ebib27","doi-asserted-by":"publisher","first-page":"63","DOI":"10.1118\/1.597525","type":"journal-article","article-title":"Fetal dose from radiotherapy with photon beams: report of AAPM Radiation Therapy Committee Task Group No 36","volume":"22","author":"Stovall","year":"1995","journal-title":"Med. Phys."},{"key":"pmbaeaf3ebib28","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/S0146-6453(01)00017-3","type":"journal-article","article-title":"Pregnancy and medical radiation, The International Commission on Radiological Protection, Publication 84","volume":"30","author":"Valentin","year":"2000","journal-title":"Ann. ICRP"},{"key":"pmbaeaf3ebib29","doi-asserted-by":"publisher","DOI":"10.1016\/j.radmeas.2024.107214","type":"journal-article","article-title":"Secondary neutrons in proton and light ion beam therapy: a review of current status, needs and potential solutions","volume":"176","author":"Vedelago","year":"2024","journal-title":"Radiat. Meas."},{"key":"pmbaeaf3ebib30","doi-asserted-by":"publisher","first-page":"366","DOI":"10.1120\/jacmp.v17i5.6327","type":"journal-article","article-title":"Spot scanning proton therapy minimizes neutron dose in the setting of radiation therapy administered during pregnancy","volume":"17","author":"Wang","year":"2016","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"pmbaeaf3ebib31","doi-asserted-by":"publisher","DOI":"10.1016\/j.phro.2025.100721","type":"journal-article","article-title":"Out-of-field dose assessment for pencil beam scanning proton radiotherapy versus photon radiotherapy for breast cancer in pregnant women","volume":"33","author":"Weessies","year":"2025","journal-title":"Phys. Imaging Radiat. Oncol."},{"key":"pmbaeaf3ebib32","doi-asserted-by":"publisher","DOI":"10.1016\/j.ejmp.2022.102513","type":"journal-article","article-title":"A review on fetal dose in Radiotherapy: a historical to contemporary perspective","volume":"105","author":"Wong","year":"2023","journal-title":"Phys. Medica"},{"key":"pmbaeaf3ebib33","doi-asserted-by":"publisher","DOI":"10.1088\/1361-6560\/ac4b38","type":"journal-article","article-title":"Fetal dose from proton pencil beam scanning craniospinal irradiation during pregnancy: a Monte Carlo study","volume":"67","author":"Yeom","year":"2022","journal-title":"Phys. Med. Biol."},{"key":"pmbaeaf3ebib34","doi-asserted-by":"publisher","DOI":"10.1088\/1361-6560\/ac5b9c","type":"journal-article","article-title":"Joint EURADOS WG9-WG11 rem-counter intercomparison in a Mevion S250i proton therapy facility with Hyperscan pulsed synchrocyclotron","volume":"67","author":"Zorloni","year":"2022","journal-title":"Phys. Med. Biol."}],"container-title":["Physics in Medicine &amp; Biology"],"original-title":[],"link":[{"URL":"https:\/\/iopscience.iop.org\/article\/10.1088\/1361-6560\/aeaf3e","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/iopscience.iop.org\/article\/10.1088\/1361-6560\/aeaf3e\/pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/iopscience.iop.org\/article\/10.1088\/1361-6560\/aeaf3e\/pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/iopscience.iop.org\/article\/10.1088\/1361-6560\/aeaf3e\/pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T07:06:53Z","timestamp":1792048013000},"score":1,"resource":{"primary":{"URL":"https:\/\/iopscience.iop.org\/article\/10.1088\/1361-6560\/aeaf3e"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,15]]},"references-count":34,"journal-issue":{"issue":"20","published-online":{"date-parts":[[2026,10,15]]},"published-print":{"date-parts":[[2026,10,28]]}},"URL":"https:\/\/doi.org\/10.1088\/1361-6560\/aeaf3e","relation":{},"ISSN":["0031-9155","1361-6560"],"issn-type":[{"value":"0031-9155","type":"print"},{"value":"1361-6560","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,10,15]]},"assertion":[{"value":"Practical considerations in measuring out-of-field neutron dose for pulsed and gantry-mounted proton therapy machines","name":"article_title","label":"Article Title"},{"value":"Physics in Medicine & Biology","name":"journal_title","label":"Journal Title"},{"value":"paper","name":"article_type","label":"Article Type"},{"value":"\u00a9 2026 The Author(s). Published on behalf of Institute of Physics and Engineering in Medicine by IOP Publishing Ltd","name":"copyright_information","label":"Copyright Information"},{"value":"2026-06-18","name":"date_received","label":"Date Received","group":{"name":"publication_dates","label":"Publication dates"}},{"value":"2026-10-01","name":"date_accepted","label":"Date Accepted","group":{"name":"publication_dates","label":"Publication dates"}},{"value":"2026-10-15","name":"date_epub","label":"Online publication date","group":{"name":"publication_dates","label":"Publication dates"}}]}}