Experimental assessment of a phosphor model for estimating the relative extrinsic efficiency in radioluminescent detectors |
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| Institution: | 1. Department of Medical Physics & Nuclear Medicine, Karolinska University Hospital, S-171 76 Stockholm, Sweden;2. Department of Radiation Physics, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden;1. Radiation Applications Research School, Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 11365-3486, Tehran, Iran;2. Department of Radiotherapy, Seyed Alshohada Radiotherapy Center, Isfahan, Iran;1. University Federico II, Post Graduate School in Medical Physics, Department of Advanced Biomedical Sciences, Napoli, Italy;2. National Research Council (CNR), Institute of Biostructures and Bioimaging, Napoli, Italy;3. University Federico II, Department of Advanced Biomedical Sciences, Napoli, Italy;4. University Hospital Federico II, Unit of Medical Physics and Radioprotection, Napoli, Italy;5. University Federico II, Department of Neurosciences, Reproductive Sciences and Dentistry, Napoli, Italy;6. University Federico II, Eye Clinic Department of Public Health, Napoli, Italy;1. Department of Radiotherapy, University Hospital Essen, Hufelandstraße 55, 45147 Essen, Germany;2. Department of Radiology, Charité – Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany;3. Department of Physics, University of Osijek, Trg Ljudevita Gaja 6, 31000 Osijek, Croatia;4. Clinic and Polyclinic for Diagnostic and Interventional Radiology, University Hospital Leipzig, Liebigstraße 20, 04103 Leipzig, Germany;1. National and Kapodistrian University of Athens, Medical School, Department of Medical Physics, Greece;2. Bioiatriki, Athens, Greece;1. Department of Clinical Radiology, Kagawa University Hospital, Kagawa, Japan;2. Graduate School of Medicine, Kagawa University, Kagawa, Japan;3. Department of Radiation Oncology, Kagawa University Hospital, Kagawa, Japan;1. Department of Physics, Carleton University, Ottawa, ON, Canada;2. Department of Medical Physics, The Ottawa Hospital Cancer Center, Ottawa, ON, Canada |
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| Abstract: | Optimising phosphor screens in dose detectors or imaging sensor designs is a cumbersome and time- consuming work normally involving specialised measuring equipment and advanced modelling. It is known that crucial optical parameters of the same phosphor may vary within a wide range of values. The aim of this work was to experimentally assess a simple previously published model where the case specific optical parameters (scattering and absorption) are instead represented by a fixed, single parameter, the light extinction factor, ξ. The term extrinsic efficiency, N, of a phosphor is also introduced, differing from the common denotation “absolute efficiency”, after noting that unknown factors (such as temperature dependence) can have an influence during efficiency estimations and hence difficult to claim absoluteness. N is expressed as the ratio of light energy emitted per unit area at the phosphor surface to incident x-ray energy fluence. By focusing on ratios and relative changes in this study, readily available instruments in a Medical Physics Department (i.e. a photometer) could be used.The varying relative extrinsic efficiency for an extended range of particle sizes (7.5 and 25 µm) and layer thicknesses (220 to 830 µm) were calculated in the model from the input parameters: the mean particle size of the phosphor, the layer thickness, the light extinction factor and the calculated energy imparted to the layer. In-house manufactured screens (Gd2O2S:Tb) were used for better control of design parameters. The model provided good qualitative agreement to experiment with quantitative deviations in relative extrinsic efficiency within approximately 2%. |
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| Keywords: | Energy transport Extrinsic efficiency Fluorescence Optimisation Phosphor model Radioluminescence |
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