In-Phantom Spectra and Dose Distributions from a High-Energy Neutron Therapy Beam
| Autor: | Eric J. Pitcher, Francesco D'Errico, J.M. Denis, Ravinder Nath, Jean-Pierre Meulders, Sylvie Benck |
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| Jazyk: | angličtina |
| Rok vydání: | 2002 |
| Předmět: |
Physics
Nuclear and High Energy Physics medicine.medical_specialty Equivalent dose Quantitative Biology::Tissues and Organs Physics::Medical Physics Dose profile Percentage depth dose curve Nuclear physics Kerma Neutron flux Absorbed dose Ionization chamber medicine Dosimetry Medical physics Nuclear Experiment Instrumentation |
| Popis: | 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 x 10 cm(2) 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. (C) 2002 Elsevier Science B.V. All rights reserved. |
| Databáze: | OpenAIRE |
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