Measurement of the modulation transfer function of digital X-ray detectors with an opaque edge-test device |
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Authors: | Illers Hartmut Buhr Egbert Günther-Kohfahl Susanne Neitzel Ulrich |
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Affiliation: | Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany. hartmut.illers@gsf.de |
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Abstract: | A variant of the edge method for the determination of the pre-sampled modulation transfer function (MTF) of digital X-ray imaging devices has been developed and accepted as the standard method in the novel DQE measurement standard IEC 62220-1. An opaque tungsten edge-test device accomplishes the ideal step-like profile of the incident X rays. The edge spread function is measured over a large region across the edge transition that enables an accurate MTF measurement including the 'low-frequency drop'. The method has been applied to different state-of-the-art X-ray imaging detectors, a computed radiography, a CsI-based indirect and an Se-based direct flat-panel detector. The MTF measurement results will be presented. In contrast to the opaque edge device, the commonly used semi-transparent edge-test devices produce scatter radiation that deteriorates the incident X-ray profile, which leads to a systematic overestimation of the MTF. |
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