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      Radiological properties of nanocomposite Fricke gel dosimeters for heavy ion beams

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          Abstract

          The radiological properties of nanocomposite Fricke gel (NC-FG) dosimeters prepared with different concentrations of nano-clay, perchloric acid and ferrous ions in deaerated conditions were investigated under carbon and argon ion beam irradiation covering a linear-energy-transfer (LET) range of 10 to 3000 eV/nm. We found that NC-FG exhibits radiological properties distinct from those of conventional Fricke gel. The radiation sensitivity of NC-FG is independent of the LET and is nearly constant even at very high LET (3000 eV/nm) values in the Bragg peak region of the argon ion beam. In addition, whereas conventional Fricke gel dosimeters only operate under acidic conditions, NC-FG dosimeters function under both acidic and neutral conditions. The radiation sensitivity decreases with decreasing nano-clay concentration in NC-FG, which indicates that the nano-clay plays a vital role in the radiation-induced oxidation of Fe 2+.

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          Most cited references26

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          Polymer gel dosimetry.

          Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.
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            Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy.

            The irradiation system and biophysical characteristics of carbon beams are examined regarding radiation therapy. An irradiation system was developed for heavy-ion radiotherapy. Wobbler magnets and a scatterer were used for flattening the radiation field. A patient-positioning system using X ray and image intensifiers was also installed in the irradiation system. The depth-dose distributions of the carbon beams were modified to make a spread-out Bragg peak, which was designed based on the biophysical characteristics of monoenergetic beams. A dosimetry system for heavy-ion radiotherapy was established to deliver heavy-ion doses safely to the patients according to the treatment planning. A carbon beam of 80 keV/microm in the spread-out Bragg peak was found to be equivalent in biological responses to the neutron beam that is produced at cyclotron facility in National Institute Radiological Sciences (NIRS) by bombarding 30-MeV deuteron beam on beryllium target. The fractionation schedule of the NIRS neutron therapy was adapted for the first clinical trials using carbon beams. Carbon beams, 290, 350, and 400 MeV/u, were used for a clinical trial from June of 1994. Over 300 patients have already been treated by this irradiation system by the end of 1997.
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              Measurement of radiation dose distributions by nuclear magnetic resonance (NMR) imaging.

              A method is described for determining the spatial distribution of radiation dose in a tissue-equivalent phantom using nuclear magnetic resonance imaging. The conversion of ferrous ions to ferric by ionising radiation alters the magnetic moment and electron spin relaxation times of the metal ion. The spin relaxation times (T1 and T2) of the hydrogen nuclei in an aqueous solution of a ferrous salt are consequently reduced substantially. These changes in T1 and T2 can be measured using standard NMR techniques. The same conversion is used in conventional Fricke dosimetry, which can be used to calibrate the technique.
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                Author and article information

                Journal
                J Radiat Res
                J. Radiat. Res
                jrr
                jrr
                Journal of Radiation Research
                Oxford University Press
                0449-3060
                1349-9157
                June 2016
                21 June 2016
                21 June 2016
                : 57
                : 3
                : 318-324
                Affiliations
                [1 ]Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
                [2 ]Department of Nuclear Engineering and Management, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
                [3 ]Department of Neurosurgery, Himon'ya Hospital , 2-9-5 Minami, Meguro-ku, Tokyo 152-0013, Japan
                [4 ]Advanced Center for Computing and Communication, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
                [5 ]Research Center for Charged Particle Therapy, National Institute of Radiological Sciences , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
                Author notes
                [* ]Corresponding author. Tel: 048-467-9463; E-mail: maeyama@ 123456riken.jp
                Article
                rrw025
                10.1093/jrr/rrw025
                4915547
                26968632
                828db06d-3d37-4a18-a4d8-f66c238200a8
                © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

                History
                : 6 December 2015
                : 4 February 2016
                : 9 February 2016
                Funding
                Funded by: Journal of Radiation Research as this article was a recipient of the JRR Award
                Award ID: ICRR 2015
                Categories
                Regular Paper

                Oncology & Radiotherapy
                ion beam,let,nanocomposite gel,gel dosimeter
                Oncology & Radiotherapy
                ion beam, let, nanocomposite gel, gel dosimeter

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