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Area and Individual Radiation Monitoring
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Radiation exposure can be external or internal. However, since sealed radioactive sources and particle accelerators are typically used in radiotherapy, all exposures can be considered external. External radiation doses to an individual result from exposure to external sources of ionizing radiation, that is, radiation sources outside the body [1]. Gamma rays, x-rays, high-energy beta particles, protons, and neutrons are considered “penetrating radiation” and present an external exposure hazard. Conversely, low-energy beta particles and alpha particles are relatively “non-penetrating” and present less of an external radiation exposure hazard. Neutrons are produced in particle therapy facilities, therapy linear accelerators (linacs), fast neutron therapy facilities, and boron neutron capture therapy (BNCT) facilities. Particle therapy facilities (heavy ions) produce neutrons with maximum energies in the GeV range [2]. Proton therapy facilities produce neutrons with energies as high as the primary proton beam energy (∼250 MeV). Typically, either cyclotrons or synchrotrons are used in these facilities. Fast neutron therapy facilities produce neutrons with energies between 50 MeV and 70 MeV. These neutron therapy beams are produced by reactors, cyclotrons, and linear accelerators. BNCT uses epithermal neutrons for therapy. The neutron source for epithermal radiation is generated from nuclear reactors and accelerator-based neutron sources (ABNS).
Particle Interactions with Matter
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
Neutrons, being uncharged particles, do not undergo interactions mediated by the Coulomb force. Instead they deposit energy via capture and collisions. For a full description of this topic see the video, but a few key points are the following: There are two energy regimes: (1) “thermal” neutrons (energies ≲0.025 eV), where the interactions are a capture mostly by H or N. (2) Fast neutrons (energies ≳100 eV), where the interactions are “billiard ball” collisions with the nucleus. After such a collision, the nucleus travels off and deposits dose through charged particle interactions.Neutrons are produced in photon therapy beams with energies >10 MV. These neutrons from interactions of photons with a high-Z material in the linear accelerator. Neutrons are also produced in proton therapy beams.A few beamlines are available in the world for neutron therapy. Boron neutron capture therapy (BNCT) is one modality for enhancing the effect, due to the high interaction cross-section of boron. The boron nucleus captures the neutron and a high-LET alpha particle is created which deposits dose.
Partial Body Neutron Activation — Truncal
Published in Stanton H. Cohn, Non-Invasive Measurements of Bone Mass and Their Clinical Application, 2020
Kenneth G. McNeill, Joan E. Harrison
A technique which cannot be of general application, but which nevertheless holds significant potential, is that of PBNAA secondary to neutron therapy in cancer patients.18 In the locally irradiated area, the neutron dose may be about 1000 times that given in routine PBNAA. The relatively high resultant activity of the body makes possible the use of low sensitivity but high resolution Ge(Li) detectors to study the gamma rays emitted by the body. Indeed, the detector need not be shielded if only the gamma rays from 49Ca, 38C1, and 24Na are to be seen, and the counting time need be only about 3 min. Longer counting times may result in information being obtained on other elements in the tumor and its immediate surroundings.
Response of murine neural stem/progenitor cells to gamma-neutron radiation
Published in International Journal of Radiation Biology, 2022
Galina A. Posypanova, Marya G. Ratushnyak, Yuliya P. Semochkina, Alexander N. Strepetov
The aim of this work was to study the sensitivity of cultured murine NSCs/NPCs to the reactor gamma-neutron irradiation (γ,n-irradiation) in a wide dose range (from 25 mGy to 2 Gy) and the features of the formation and repair of DNA DSB in these cells. Neutrons are electrically neutral high-energy particles that produce more severe damage to DNA than photons do; therefore they are more efficient in the therapy of radioresistant tumors. Neutron relative biological effectiveness (RBE) varies from 1 to 10 depending on the kind of tissue, neutron energy, and the parameter explored (Scott and Pandita 2006). The advantage of using fast neutron to eliminate radioresistant cells lies partially in the lesser dependency on cell oxygenation, cell cycle parameters, and proliferation rate (Rockhill and Laramore 2016; Goodhead 2019; Jones 2020). The effective use of neutrons in radiation therapy increases interest in the study of the mechanisms of action of neutron radiation to develop the methods of protection for normal tissues and optimize radiotherapy regimens (Goodhead 2019) since neutron therapy significantly increases the risks of long-term post-radiation complications.
Neutrons are forever! Historical perspectives
Published in International Journal of Radiation Biology, 2019
Neutron radiobiology has continued as a vigorous field of study throughout the past 84 years. Three main driving forces have been a concern for protection from the harmful biological effects of neutrons, exploitation and optimization of the tumor sterilizing effectiveness of neutrons for cancer therapy, and scientific curiosity. The degree of effort has fluctuated as emphasis has shifted from time to time, but all three forces remain active today. Whatever the future holds for the various types of neutron therapy, the health protection aspects will remain with us permanently because of natural environmental exposure to neutrons, notably from cosmic rays, as well as increased additional exposures from a variety of human activities.
A novel vertebrate system for the examination and direct comparison of the relative biological effectiveness for different radiation qualities and sources
Published in International Journal of Radiation Biology, 2018
E. R. Szabó, Z. Reisz, R. Polanek, T. Tőkés, Sz. Czifrus, Cs. Pesznyák, B. Biró, A. Fenyvesi, B. Király, J. Molnár, Sz. Brunner, B. Daroczi, Z. Varga, K. Hideghéty
In recent years, there has been a marked development of radiation techniques that have contributed to the improvement of cancer treatment outcome (Peeters et al. 2010; Allemani et al. 2015). Advanced photon delivery techniques with enhanced conformity and the rapidly growing installations of superconducting cyclotron/synchrotron-based particle therapy facilities have made hadron therapy available for an increasing number of cancer patients (Specht et al. 2015). Charged particle therapy leads to an increase in dose precision due to the energy deposition characterized by the Bragg peak. Further innovative radiation approaches including boron neutron capture therapy (BNCT, Barth et al. 2012), high power laser-driven pulsed, ultra-intense, very high energy electron therapy (VHEE, Schüler et al. 2017), medical microbeam irradiation (Bräuer-Krisch et al. 2015) and Boron Proton Fusion Enhanced Proton therapy (BPFEPT, Yoon et al. 2014) are under scientific evaluation in order to improve the therapeutic ratio. It is therefore essential to study the biological effects of the different ionizing radiation forms and to establish safe clinical applications. The biological properties of any type of radiation are derived from the energy deposition pattern, which defines the properties and amount of DNA damage and potential repair. The energy deposited per unit track linear energy transfer (LET) is measured in keV/μm. The relative biological effectiveness (RBE) is defined in relation to a reference photon irradiation and is influenced by many factors. High LET, and consequently high RBE, radiation combined with a high selectivity of dose deposition has tremendous advantages over low LET beams for the local control for radio-resistant, hypoxic tumors – even in critical anatomical location. One of the first large clinical scale attempts to use high RBE radiation was fast neutron therapy in the 70s and 80s (Specht et al. 2015). Highly contradictory results were obtained at these first generation neutron facilities and actually only four fast neutron facilities with improved delivery technique (3D planning, conformal/intensity-modulated RT) offering fast neutron therapy (FNT) for patients with salivary gland tumors, sarcomas and malignant melanoma (Liao et al. 2014).