In-phantom spectra and dose distributions from a high-energy neutron therapy beam |
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| Affiliation: | 1. Institut de Physique Nucléaire, Université Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve, Belgium;2. Department of Therapeutic Radiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA;3. Manuel Lujan, Jr. Neutron Scattering Center, Los Alamos National Laboratory, Box 1663, MS H816, Los Alamos, NM 87545, USA;1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, School of Renewable Energy, North China Electric Power University, Beijing, 102206, China;2. Beijing Key Laboratory of Urban Oil and Gas Distribution Technology, China University of Petroleum-Beijing, Fuxue Road No. 18, Changping District, Beijing, 102249, China;3. Key Lab of Agricultural Water and Soil Engineering of Education Ministry, Northwest A&F University, Yangling, 712100, PR China;4. National & Local Joint Engineering Research Center of Harbor Oil & Gas Storage and Transportation Technology/Zhejiang Key Laboratory of Petrochemical Environmental Pollution Control, Zhejiang Ocean University, No.1 Haida South Road, 316022, Zhoushan, PR China;1. School of Energy and Power Engineering, Beihang University, Beijing 100191, China;2. Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191, China;3. Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191, China;4. Hunan Aviation Powerplant Research Institute, Aero Engine (Group) Corporation of China, Zhuzhou 412002, China;5. Aero Engine Academy of China, Aero Engine (Group) Corporation of China, Beijing 101304, China;1. Future Technology Center, Corporate R&D, LG Chem, Ltd., 188, Munji-ro, Yuseong-gu, Daejeon, 305-380, Republic of Korea;2. Department of Advanced Materials and Chemical Engineering, Hannam University, 1646 Yuseong-daero, Yuseong-gu, Daejeon, 34054, Republic of Korea;1. School of Chemical Engineering, University of Birmingham, Edgbaston B15 2TT, United Kingdom;2. Industrial Tomography Systems PLC, Manchester M3 3JZ, United Kingdom;1. Department of Nuclear Physics and its Applications, Institute of Physics, Silesian University, 4 Uniwersytecka Str., 40-007 Katowice, Poland;2. Department of Medical Physics, Centre of Oncology, Gliwice Branch, 15 Wybrzeże Armii Krajowej Str., 44-100 Gliwice, Poland |
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| Abstract: | In radiotherapy with external beams, healthy tissues surrounding the target volumes are inevitably irradiated. In the case of neutron therapy, the estimation of dose to the organs surrounding the target volume is particularly challenging, because of the varying contributions from primary and secondary neutrons and photons of different energies. The neutron doses to tissues surrounding the target volume at the Louvain-la-Neuve (LLN) facility were investigated in this work. At LLN, primary neutrons have a broad spectrum with a mean energy of about 30 MeV. The transport of a 10×10 cm2 beam through a water phantom was simulated by means of the Monte Carlo code MCNPX. Distributions of energy-differential values of neutron fluence, kerma and kerma equivalent were estimated at different locations in a water phantom. The evolution of neutron dose and dose equivalent inside the phantom was deduced. Measurements of absorbed dose and of dose equivalent were then carried out in a water phantom using an ionization chamber and superheated drop detectors (SDDs). On the beam axis, the calculations agreed well with the ionization chamber data, but disagreed significantly from the SDD data due to the detector's under-response to neutrons above 20 MeV. Off the beam axis, the calculated absorbed doses were significantly lower than the ionization chamber readings, since gamma fields were not accounted for. The calculated data are doses from neutron-induced charge particles, and these agreed with the values measured by the photon-insensitive SDDs. When exposed to the degraded spectra off the beam axis, the SDD offered reliable estimates of the neutron dose equivalent. |
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