Monte Carlo determination of a nanoDot OSLD response using quality index for diagnostic kilovoltage X-ray beams |
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| Institution: | 1. LIP-Coimbra, Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal;2. Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal;1. Department of Medical Physics, Hospital Universitario Ramón y Cajal, Madrid, Spain;2. Biomedical Engineering, ETSIT, Universidad Politécnica de Madrid, Madrid, Spain;3. Medical Physics, Department of Radiology, Rehabilitation and Physiotherapy, Universidad Complutense de Madrid, Madrid, Spain;1. Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Italy;2. Università Cattolica del Sacro Cuore, Rome, Italy;1. Fondazione Policlinico Universitario ‘‘A. Gemelli’’ IRCCS, Roma, Italy;2. Università Cattolica del Sacro Cuore, Rome, Italy;1. Department of Radiology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo 105-8470, Japan;2. Department of Radiological Technology, Tohoku University Graduate School of Medicine, 2-1 Seiryo, Aoba-ku, Sendai, Miyagi 980-8575, Japan;3. Okinaka Memorial Institute for Medical Research, 2-2-2 Toranomon, Minato-ku, Tokyo 105-8470, Japan;4. Department of Radiological Health Science, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, 1-1, Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan;5. Department of Endovascular Neurosurgery, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo 105-8470, Japan |
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| Abstract: | PurposeThis study aims to investigate the energy response of an optically stimulated luminescent dosimeter known as nanoDot for diagnostic kilovoltage X-ray beams via Monte Carlo calculations.MethodsThe nanoDot response is calculated as a function of X-ray beam quality in free air and on a water phantom surface using Monte Carlo simulations. The X-ray fluence spectra are classified using the quality index (QI), which is defined as the ratio of the effective energy to the maximum energy of the photons. The response is calculated for X-ray fluence spectra with QIs of 0.4, 0.5, and 0.6 with tube voltages of 50–137.6 kVp and monoenergetic photon beams. The surface dose estimated using the calculated response is verified by comparing it with that measured using an ionization chamber.ResultsThe nanoDot response in free air for monoenergetic photon beams (QI = 1.0) varies significantly at photon energies below 100 keV and reaches a factor of 3.6 at 25–30 keV. The response differs by up to approximately 6% between QIs of 0.4 and 0.6 for the same half-value layer (HVL). The response at the phantom surface decreases slightly owing to the backscatter effect, and it is almost independent of the field size. The agreement between the surface dose estimated using the nanoDot and that measured using the ionization chamber for assessing X-ray beam qualities is less than 2%.ConclusionsThe nanoDot response is indicated as a function of HVL for the specified QIs, and it enables the direct surface dose measurement. |
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| Keywords: | NanoDot OSLD Energy response Quality index Kilovoltage X-ray beam |
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