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Proceedings Paper

Performance of a CsI:TL-screen-based scanning slot detector for digital mammography
Author(s): Zhenxue Jing; Walter Huda; James K. Walker; Won Y. Choi
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Paper Abstract

Thallium activated CsI scintillation screen (CsI:Tl) has advantages over rare-earth phosphor screens when used in a scanning slot x-ray detector for digital mammography. The scintillation decay time for CsI:Tl is only approximately 1 microsecond(s) which eliminates the afterglow effect associated with the use of rare-earth phosphor. The CsI needles serve to limit the spread of the scintillation light which permits the use of a relatively thick CsI:Tl screen to improve detector x-ray interaction efficiency without sacrificing resolution performance. A prototype scanning slot detector was made of a CsI:Tl screen and was optically coupled to two CCDs by plastic optical fiber image guides. The screen was composed of prismatic CsI crystals with a needle size of approximately 5 micrometers . Image guides used in the detector had an input to output ratio of 1:1, and were made of 10 micrometers diameter plastic optical fibers. Each CCD, operated in the time-delayed integration mode, was an 1100 X 330 pixel array with pixel size of 24 micrometers . A full scale scanning slot detector will contain eight rather than two such modules. The x-ray interaction efficiency of the slot x-ray detector was calculated to be approximately 84 percent at 20 keV for the CsI:Tl screen, and was approximately 20 percent greater than that of a 31.7 mg/cm2 thick Gd2O2S:Tb phosphor screen. Limiting spatial resolution was investigated by taking the images of a 1 degree star resolution test pattern as a function of detector scan speed. Limiting spatial resolution was approximately 15 1p/mm at a scan speed of 4 cm/s and improved only slightly to approximately 16 1p/mm as the scanning speed decreased to 1 cm/s.

Paper Details

Date Published: 2 May 1997
PDF: 7 pages
Proc. SPIE 3032, Medical Imaging 1997: Physics of Medical Imaging, (2 May 1997); doi: 10.1117/12.273994
Show Author Affiliations
Zhenxue Jing, Univ. of Florida (United States)
Walter Huda, Univ. of Florida (United States)
James K. Walker, Nanoptics, Inc. (United States)
Won Y. Choi, Nanoptics, Inc. (United States)

Published in SPIE Proceedings Vol. 3032:
Medical Imaging 1997: Physics of Medical Imaging
Richard L. Van Metter; Jacob Beutel, Editor(s)

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