31 March 2016 Exploration of maximum count rate capabilities for large-area photon counting arrays based on polycrystalline silicon thin-film transistors
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Abstract
Pixelated photon counting detectors with energy discrimination capabilities are of increasing clinical interest for x-ray imaging. Such detectors, presently in clinical use for mammography and under development for breast tomosynthesis and spectral CT, usually employ in-pixel circuits based on crystalline silicon – a semiconductor material that is generally not well-suited for economic manufacture of large-area devices. One interesting alternative semiconductor is polycrystalline silicon (poly-Si), a thin-film technology capable of creating very large-area, monolithic devices. Similar to crystalline silicon, poly-Si allows implementation of the type of fast, complex, in-pixel circuitry required for photon counting – operating at processing speeds that are not possible with amorphous silicon (the material currently used for large-area, active matrix, flat-panel imagers). The pixel circuits of two-dimensional photon counting arrays are generally comprised of four stages: amplifier, comparator, clock generator and counter. The analog front-end (in particular, the amplifier) strongly influences performance and is therefore of interest to study. In this paper, the relationship between incident and output count rate of the analog front-end is explored under diagnostic imaging conditions for a promising poly-Si based design. The input to the amplifier is modeled in the time domain assuming a realistic input x-ray spectrum. Simulations of circuits based on poly-Si thin-film transistors are used to determine the resulting output count rate as a function of input count rate, energy discrimination threshold and operating conditions.
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Albert K. Liang, Martin Koniczek, Larry E. Antonuk, Youcef El-Mohri, Qihua Zhao, "Exploration of maximum count rate capabilities for large-area photon counting arrays based on polycrystalline silicon thin-film transistors", Proc. SPIE 9783, Medical Imaging 2016: Physics of Medical Imaging, 97833O (31 March 2016); doi: 10.1117/12.2216944; https://doi.org/10.1117/12.2216944
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