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Proceedings Paper

Investigation of random gain variations in columnar CsI:Tl using single x-ray photon imaging
Author(s): Adrian Howansky; A. R. Lubinsky; S. K. Ghose; Katsuhiko Suzuki; Wei Zhao
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Paper Abstract

The x-ray imaging performance of an indirect flat panel detector (I-FPD) is degraded by random variations in its scintillator’s conversion gain. At energies below the K-edge, these variations are caused by depth-dependence in light collection from within the scintillator, and intrinsic fluctuations in the number of optical photons (Nph) emitted per absorbed x-ray. At fixed energy, the former effect can be quantified by the average depth-dependent gain Nph (𝑧). The latter effect can be evaluated using a Fano factor FN, defined as the variance in Nph divided by its mean at fixed interaction depth. Neither phenomenon has been directly measured in non-transparent scintillators used in medical I-FPDs, namely columnar CsI:Tl. This work presents experimental measurements of Nph(𝑧) and FN in a columnar CsI:Tl scintillator with 1000 μm thickness. X-ray interactions were localized to fixed depths (±10 μm, 100 μm intervals) in the scintillator using a microslit beam of parallel synchrotron radiation (32 keV). Light bursts from single interactions at each depth were imaged using an II-EMCCD optical camera, and their magnitude was characterized by 2D summation of their image pixel values. The II-EMCCD camera was calibrated to convert summed pixel values to numbers of optical photons detected per event. The number distributions of photons collected per event were represented in histograms as “depth-localized pulse height spectra” (DLPHS), from which𝑁̅ph (𝑧) and FN were derived. The II-EMCCD’s noise contribution to these measurements was estimated and removed from FN. Depth-dependent and intrinsic variations in the gain of columnar CsI:Tl are compared.

Paper Details

Date Published: 9 March 2018
PDF: 10 pages
Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 105730O (9 March 2018); doi: 10.1117/12.2293849
Show Author Affiliations
Adrian Howansky, Stony Brook Univ. (United States)
A. R. Lubinsky, Stony Brook Univ. (United States)
S. K. Ghose, Brookhaven National Lab. (United States)
Katsuhiko Suzuki, Hamamatsu Photonics K.K. (Japan)
Wei Zhao, Stony Brook Univ. (United States)

Published in SPIE Proceedings Vol. 10573:
Medical Imaging 2018: Physics of Medical Imaging
Joseph Y. Lo; Taly Gilat Schmidt; Guang-Hong Chen, Editor(s)

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