文章基本信息

标题：Energy Dependent Imaging Properties of the Medipix2 X-ray Detector
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作者：T. Michel
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2007
卷号：2007
出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The first part of this contribution covers simulation studies and measurements of imaging properties of the Medipix2 detector. Position resolving properties of the Medipix-detectors described by the so-called modulation transfer function (MTF) in dependence on the discriminator threshold and on primary energy will be discussed. The MTF shows a significant drop at low spatial frequencies due to the emission and detection of fluorescence photons from the backside, e.g. the bump-bonds and the silver containing glue between the ASIC and the chipboard. The second part is focused on the energy resolving properties of the Medipix detectors and their exploitation in X-ray imaging. Simulation results of the monoenergetic response functions, taking diffusion in the sensor layer and backscattering from the chipboard into account, are in good agreement with measurements. Two methods have been developed to calculate the impinging energy spectrum with the measured energy deposition spectrum. These methods allow the determination of the material composition of an irradiated object. The successive application of the pseudo-inverse of an attenuation coefficient matrix of known materials on the reconstructed transmitted spectrum in each pixel gives quantitative values of the material concentration in the object. The determination of material concentrations of a phantom comprising several materials is shown in a measurement. The Medipix3 with its socalled color mode will offer excellent possibilities to use this method.