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Medical and Biological Applications of Low Energy Accelerators
Published in Vlado Valković, Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
We shall discuss in some details the particle therapy in Japan where the pioneer work of the particle therapy by cyclotron began at NIRS in 1975. Fast neutrons and protons have been used for cancer treatments. The results for fast neutron therapy were not so excellent and the energy of the proton beam was not enough for the treatment of thick tissue. Higher energy proton therapy begun at the Tsukuba University with proton beams from the 500 MeV booster synchrotron of the 12 GeV KEK proton synchrotron.
Area and Individual Radiation Monitoring
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
The commonly used Andersson–Braun (AB) rem-meter has a cylindrical polyethylene moderator surrounding a BF3 counter tube [33]. Its energy response closely follows the NCRP 38 dose equivalent conversion function (from thermal to about 10 MeV), except at intermediate energies where it over responds. The counter tube is surrounded by a borated plastic sleeve which minimizes its over-response in the 10 keV to 100 keV range. The response at thermal energies is increased because of holes drilled in the sleeve. However, the directional response of the rem-meter is impacted by its cylindrical moderator geometry. According to Cosack and Leisecki [34], a change in response with instrument orientation of as much as 35% has been observed for neutron energy of 1 MeV. When the rem-meter is exposed with its side oriented to a source of thermal neutrons, a 65% underestimation in the true dose equivalent has been observed. A modified version with a spherical polyethylene moderator and a cadmium layer was designed by Hankins in order to improve the directional dependence [35]. It is currently marketed by Thermo Fisher Scientific as the model NRD. However, the high-energy response of the NRD decreases steadily at energies above 7 MeV. At these energies, the neutron fluence is considerably reduced for therapy linacs. Therefore, the rem-meter can still be used. However, it cannot be used for particle therapy and fast neutron therapy facilities, because of the higher-energy neutrons that are encountered at such facilities.
Clinical Aspects of Head and Neck Cancer
Published in Loredana G. Marcu, Iuliana Toma-Dasu, Alexandru Dasu, Claes Mercke, Radiotherapy and Clinical Radiobiology of Head and Neck Cancer, 2018
Loredana G. Marcu, Iuliana Toma-Dasu, Alexandru Dasu, Claes Mercke
As an alternative to surgery, radiotherapy as a single modality treatment has also been reported to lead to significant long-term benefits (Chen 2006). However, one of the most successful therapies for salivary gland cancers is fast neutron therapy, which offers high locoregional control and survival rates, being recommended as initial primary treatment (Douglas 1996). A report on 279 patients treated with curative intent for salivary gland cancer has been published by the University of Washington Cancer Centre team (Douglas 2003). The 6-year actuarial overall survival and locoregional control was 59%.
Hyperthermia with photon radiotherapy is thermoradiobiologically analogous to neutrons for tumors without enhanced normal tissue toxicity
Published in International Journal of Hyperthermia, 2019
Niloy Ranjan Datta, Stephan Bodis
Fast neutron therapy was introduced in 1938 with the belief that its favorable radiobiological features would help overcome some of the inherent limitations of X or γ-ray photon radiotherapy (RT) [1]. Compared with photons, fast neutron beams have a higher linear energy transfer (LET) (20–100 keV/μ for neutrons vs. 0.2–2 keV/μ with photons), a higher relative biological effectiveness (RBE) (2.5–3.0) and a lower oxygen enhancement ratio (OER) (1.4–1.7) [2–5]. However, the physical depth dose distribution profiles of both are similar [6]. The radiobiological gains with a higher LET and a higher RBE could be counterproductive with neutrons as, in contrast to protons or 12C ions, the absence of Bragg peak would lead to irradiation of the entire treatment volume with a high LET neutron beam. This could deliver unwanted higher biologically effective doses (BED) to adjacent normal tissues, resulting in higher toxicities. Thus, although a favorable tumor response has been reported for various tumor sites with neutrons, the advantage was largely offset by higher late tissue toxicities, increased risk of cancer induction and growing concerns regarding radiation protection [1,2,5,7]. These apprehensions contributed to the gradual decline in popularity of fast neutron therapy in modern RT practice.
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).