A study on the role of gelatin in methacrylic-acid-based gel dosimeters |
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| Authors: | Shin-ichiro Hayashi Munenori Yoshioka Shuji Usui Kiyofumi Haneda Takahiro Kondo Kim B McAuley Takahiro Tominaga |
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| Institution: | 1. Department of Clinical Radiology, Faculty of Health Sciences, Hiroshima International University, Higashi-Hiroshima, Hiroshima 739-2695, Japan;2. Department of Medical Physics & Engineering, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan;3. Medical Engineering and Technology, Hiroshima International University Graduate School of Integrated Human Sciences Studies, Higashi-Hiroshima, Hiroshima 739-2695, Japan;4. Department of Chemical Engineering, Queen’s University, Kingston ON, Canada K7L 3N6;2. Departamento de Física, Universidad Nacional, Heredia, Costa Rica;3. Universidad Nacional de Córdoba, Facultad de Ciencias Químicas, Departamento de Química Orgánica, Córdoba, Argentina;4. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada, IPQA, CONICET, Córdoba, Argentina;5. Instituto de Física E. Gaviola, IFEG, CONICET, Córdoba, Argentina;6. Centro de Física e Ingeniería en Medicina, CFIM & Departamento de Ciencias Físicas, Universidad de La Frontera, Temuco, Chile;2. Department of Medical Physics, Faculty of Paramedical Sciences, Ilam University of Medical Sciences, Ilam, Iran;3. Department of Avionic Engineering, Aviation Industry Training Center, Tehran, Iran;1. Physics Department, Imam Khomeini International University, Qazvin, Iran;2. Medical Imaging Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran;1. Radiation Technology Center, Atomic Energy Research Institute, King Abdulaziz City for Science and Technology, P.O. Box 6086, Riyadh, 11442, Saudi Arabia;2. Biomedical Physics Department, Research Center, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia;3. Polymer Chemistry Department, National Center for Radiation Research and Technology, Atomic Energy Authority, PO Box 8029, Nasr City, Cairo, Egypt;4. Radiation Protection and Dosimetry Department, National Center for Radiation Research and Technology, Atomic Energy Authority, PO Box 8029, Nasr City, Cairo, Egypt;1. Medical Imaging Department, Faculty of Applied Medical Sciences, The Hashemite University, Zarqa 13133, Jordan;2. Physics Department, Faculty of Science, The Hashemite University, Zarqa 13133, Jordan;3. Department of Radiography, Al-Hussein Bin Talal University, P.O. Box (20), Ma''an, Jordan;4. Physics Department, Faculty of Science, Yarmouk University, Irbid 21163, Jordan;5. Biomedical Engineering Department, Faculty of Engineering, The Hashemite University, Zarqa 13133, Jordan |
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| Abstract: | In radiotherapy treatment, polymer gel dosimetry can be used for verifying three-dimensional (3D) dose distributions. Gelatin is generally used as a gelling agent in the dosimeters. In this paper, another role of gelatin in a methacrylic-acid-based gel dosimeter (MAGAT) is investigated. Temperature increases due to exothermic polymerization in the irradiated gel are measured directly. Dose–R2 responses are also obtained using MRI. It is shown that no appreciable increases in either temperature or R2 are observed in MAGAT dosimeters made without gelatin, and that significant temperature and R2 increases are observed when very low gelatin concentrations are used. These results indicate that gelatin is an important enabler for radiation-induced free-radical polymerization in methacrylic-acid-based gels. When gelatin is replaced by amino acids, changes in temperature are observed, along with small changes in R2. The resulting dosimeter solutions remain transparent because the polymer does not precipitate as it does in regular MAGAT dosimeters containing gelatin. When the amino acids are replaced by acids without amino groups, no temperature or R2 changes are observed, indicating that no polymer forms. These results show that amino groups (and possibly other functional groups) on the gelatin catalyze the radiation-induced free-radical polymerization that occurs in MAGAT dosimeters. |
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