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A comprehensive spectrometry study of a stray neutron radiation field in scanning proton therapy.
Phys. Med. Biol. 61, 4127-4140 (2016)
The purpose of this study is to characterize the stray neutron radiation field in scanning proton therapy considering a pediatric anthropomorphic phantom and a clinically-relevant beam condition. Using two extended-range Bonner sphere spectrometry systems (ERBSS), Working Group 9 of the European Radiation Dosimetry Group measured neutron spectra at ten different positions around a pediatric anthropomorphic phantom irradiated for a brain tumor with a scanning proton beam. This study compares the different systems and unfolding codes as well as neutron spectra measured in similar conditions around a water tank phantom. The ten spectra measured with two ERBSS systems show a generally similar thermal component regardless of the position around the phantom while high energy neutrons (above 20 MeV) were only registered at positions near the beam axis (at 0°, 329° and 355°). Neutron spectra, fluence and ambient dose equivalent, H (*)(10), values of both systems were in good agreement (<15%) while the unfolding code proved to have a limited effect. The highest H (*)(10) value of 2.7 μSv Gy(-1) was measured at 329° to the beam axis and 1.63 m from the isocenter where high-energy neutrons (E ⩾ 20 MeV) contribute with about 53%. The neutron mapping within the gantry room showed that H (*)(10) values significantly decreased with distance and angular position with respect to the beam axis dropping to 0.52 μSv Gy(-1) at 90° and 3.35 m. Spectra at angles of 45° and 135° with respect to the beam axis measured here with an anthropomorphic phantom showed a similar peak structure at the thermal, fast and high energy range as in the previous water-tank experiments. Meanwhile, at 90°, small differences at the high-energy range were observed. Using ERBSS systems, neutron spectra mapping was performed to characterize the exposure of scanning proton therapy patients. The ten measured spectra provide precise information about the exposure of healthy organs to thermal, epithermal, evaporation and intra-nuclear cascade neutrons. This comprehensive spectrometry analysis can also help in understanding the tremendous literature data based rem-counters while also being of great value for general neutron shielding and radiation safety studies.
Impact Factor
Scopus SNIP
Web of Science
Times Cited
Times Cited
Scopus
Cited By
Cited By
Altmetric
2.811
1.648
21
23
Anmerkungen
Besondere Publikation
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Publikationstyp
Artikel: Journalartikel
Dokumenttyp
Wissenschaftlicher Artikel
Schlagwörter
Bonner Sphere Measurements; Bonner Sphere Sets; Dose-equivalent
Sprache
englisch
Veröffentlichungsjahr
2016
HGF-Berichtsjahr
2016
ISSN (print) / ISBN
0031-9155
e-ISSN
1361-6560
Zeitschrift
Physics in Medicine and Biology
Quellenangaben
Band: 61,
Heft: 11,
Seiten: 4127-4140
Verlag
Institute of Physics Publishing (IOP)
Verlagsort
Bristol
Begutachtungsstatus
Peer reviewed
Institut(e)
Institute of Radiation Protection (ISS)
POF Topic(s)
30504 - Mechanisms of Genetic and Environmental Influences on Health and Disease
Forschungsfeld(er)
Radiation Sciences
PSP-Element(e)
G-501100-001
WOS ID
WOS:000377427700015
Scopus ID
84971507015
PubMed ID
27171358
Erfassungsdatum
2016-05-18