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Proceedings Paper

An indirect flat-panel detector with avalanche gain for low dose x-ray imaging: SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout)
Author(s): Wei Zhao; Dan Li; J. A. Rowlands; N. Egami; Y. Takiguchi; M. Nanba; Y. Honda; Y. Ohkawa; M. Kubota; K. Tanioka; K. Suzuki; T. Kawai
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Paper Abstract

An indirect flat-imager with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose x-ray imaging with high resolution. It is made by optically coupling a structured x-ray scintillator CsI (Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The charge image created by HARP is read out by electron beams generated by the FEA. The proposed detector is called SAPHIRE (Scintillator Avalanche Photoconductor with HIgh Resolution Emitter readout). The avalanche gain of HARP depends on both a-Se thickness and applied electric field ESe. At ESe of > 80 V/μm, the avalanche gain can enhance the signal at low dose (e.g. fluoroscopy) and make the detector x-ray quantum noise limited down to a single x-ray photon. At high exposure (e.g. radiography), the avalanche gain can be turned off by decreasing ESe to < 70 V/μm. In this paper the imaging characteristics of the FEA readout method, including the spatial resolution and noise, were investigated experimentally using a prototype optical HARP-FEA image sensor. The potential x-ray imaging performance of SAPHIRE, especially the aspect of programmable gain to ensure wide dynamic range and x-ray quantum noise limited performance at the lowest exposure in fluoroscopy, was investigated.

Paper Details

Date Published: 18 March 2008
PDF: 11 pages
Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 69130M (18 March 2008); doi: 10.1117/12.772774
Show Author Affiliations
Wei Zhao, State Univ. of New York at Stony Brook (United States)
Dan Li, State Univ. of New York at Stony Brook (United States)
J. A. Rowlands, Sunnybrook and Women's Health Sciences Ctr. (Canada)
N. Egami, Japan Broadcasting Corp. (Japan)
Y. Takiguchi, Japan Broadcasting Corp. (Japan)
M. Nanba, Japan Broadcasting Corp. (Japan)
Y. Honda, Japan Broadcasting Corp. (Japan)
Y. Ohkawa, Japan Broadcasting Corp. (Japan)
M. Kubota, Japan Broadcasting Corp. (Japan)
K. Tanioka, Japan Broadcasting Corp. (Japan)
K. Suzuki, Hamamatsu Photonics K.K. (Japan)
T. Kawai, Hamamatsu Photonics K.K. (Japan)


Published in SPIE Proceedings Vol. 6913:
Medical Imaging 2008: Physics of Medical Imaging
Jiang Hsieh; Ehsan Samei, Editor(s)

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