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5 June 2003 Effect on DQE of screen energy weighting in mammography
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Abstract
Our work investigates the effect on the zero-spatial-frequency DQE of indirect mammographic image receptors of the combined effects of x-ray beam hardening and light photon transport within the x-ray sensitive medium of the image receptor. Beam hardening, in this context, refers to the preferential absorption of low-energy x-ray photons at the surface of the detector on which the x-ray beam is incident, with deeper layers of the detector absorbing higher and higher average energies. The light photon transport properties of both powder and crystalline/columnar phosphors favor the collection at the light-sensitive element of the detector of light photons generated closest to that element. The net result of these two effects is to perform a weighting of the detected x-ray spectrum. For the standard back-screen configuration used in conventional mammography, low-energy x rays are more heavily weighted, matching the energy dependence of the signal to be detected. For a front-screen configuration, used in all existing indirect-detection digital mammographic systems, just the opposite is true. We have used the optical Monte Carlo simulation code DETECT-II to determine average light collection efficiency and optical pulse distributions for a Min-R screen in both front- and back-screen configurations, and for two thicknesses of CsI, as a function of x-ray energy. These data, along with appropriately hardened x-ray spectra for several anode and filter combinations and a range of tube voltages, were used as input to the task-dependent DQE theory of Tapiovaara and Wagner.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Robert J. Jennings and Aldo Badano "Effect on DQE of screen energy weighting in mammography", Proc. SPIE 5030, Medical Imaging 2003: Physics of Medical Imaging, (5 June 2003); https://doi.org/10.1117/12.480198
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