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Proceedings Paper

Investigation of the screen optics of thick CsI(Tl) detectors
Author(s): Adrian Howansky; Boyu Peng; Katsuhiko Suzuki; Masanori Yamashita; A. R. Lubinsky; Wei Zhao
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Paper Abstract

Flat panel imagers (FPI) are becoming the dominant detector technology for digital x-ray imaging. In indirect FPI, the scintillator that provides the highest image quality is Thallium (Tl) doped Cesium Iodide (CsI) with columnar structure. The maximum CsI thickness used in existing FPI is ~600 microns, due to concerns of loss in spatial resolution and light output with further increase in thickness. The goal of the present work is to investigate the screen-optics for CsI with thicknesses much larger than that used in existing FPI, so that the knowledge can be used to improve imaging performance in dose sensitive and higher energy applications, such as cone-beam CT (CBCT). Columnar CsI(Tl) scintillators up to 1 mm in thickness with different screen-optical design were investigated experimentally. Pulse height spectra (PHS) were measured to determine the Swank factor at x-ray energies between 25 and 75 keV, and to derive depth-dependent light escape efficiency i.e. gain. Detector presampling MTF, NPS and DQE were measured using a high-resolution CMOS optical sensor. Optical Monte Carlo simulation was performed to estimate optical parameters for each screen design and derive depth-dependent gain and MTF, from which overall MTF and DQE were calculated and compared with measured results. The depth-dependent imaging performance parameters were then used in a cascaded linear system model (CLSM) to investigate detector performance under screen- and sensor-side irradiation conditions. The methodology developed for understanding the optics of thick CsI(Tl) will lead to detector optimization in CBCT.

Paper Details

Date Published: 18 March 2015
PDF: 12 pages
Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94120G (18 March 2015); doi: 10.1117/12.2082101
Show Author Affiliations
Adrian Howansky, Stony Brook Univ. (United States)
Boyu Peng, Stony Brook Univ. (United States)
Katsuhiko Suzuki, Hamamatsu Photonics K.K. (Japan)
Masanori Yamashita, Hamamatsu Photonics K.K. (Japan)
A. R. Lubinsky, Stony Brook Univ. (United States)
Wei Zhao, Stony Brook Univ. (United States)

Published in SPIE Proceedings Vol. 9412:
Medical Imaging 2015: Physics of Medical Imaging
Christoph Hoeschen; Despina Kontos, Editor(s)

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