Detective quantum efficiency of a CsI:Tl scintallator-based scanning slot x-ray detector for digital mammography

Zhenxue Jing; Walter Huda; James K. Walker; Won Y. Choi

doi:10.1117/12.317062

24 July 1998 Detective quantum efficiency of a CsI:Tl scintallator-based scanning slot x-ray detector for digital mammography

Zhenxue Jing, Walter Huda, James K. Walker, Won Y. Choi

Author Affiliations +

Proceedings Volume 3336, Medical Imaging 1998: Physics of Medical Imaging; (1998) https://doi.org/10.1117/12.317062
Event: Medical Imaging '98, 1998, San Diego, CA, United States

Abstract

An investigation was made of the key determinants of the detective quantum efficiency at zero spatial frequency [DQE(0)] of a CsI:Tl scintillator based scanning slot x- ray detector for digital mammography. The slot x-ray detector was made of a prismatic type thallium activated CsI scintillator (150 micrometer thick) optically coupled to CCDs by fiber optical image guides. Monte Carlo calculations were performed to generate the CsI:Tl scintillator Swank factor on the basis of the energy deposition from pencil beam x-ray sources and light transmission within the CsI:Tl scintillator. A theoretical expression for the detector DQE(0) was obtained which was used to investigate the detector imaging performance as a function of x-ray energy, x-ray exposure, CCD electronic noise level, and optical coupling efficiency of the fiber optic image guide. The Swank factor of the CsI:Tl scintillator was close to unity at x-ray energies below Iodine K-edge (33.2 keV), but decreased to approximately 0.8 at higher x-ray energies up to 40 keV. DQE(0) of the slot x-ray detector was approximately 75% at 15 keV but decreased to approximately 40% at 30 keV. Optimum DQE(0) performance of the slot x-ray detector was generally obtained at a detector x-ray exposure level above approximately 5 to 10 mR and an electronic noise level below approximately 50 electrons rms. A drop in the optical coupling efficiency of the image guide from 1.0 to 0.3 reduced the detector DQE(0) from approximately 75% to approximately 55% in the mammography x-ray energy range. The key finding in this study is that the choice of the x-ray energy has a major impact on the DQE(0) of a CsI:Tl scintillator based slot x-ray detector. Since the x-ray photon energy also affects x-ray tube loading, mean glandular dose and subject contrast, the choices of optimal x-ray spectra from current mammography x-ray tubes require further investigation.

Citation Download Citation

Zhenxue Jing, Walter Huda, James K. Walker, and Won Y. Choi "Detective quantum efficiency of a CsI:Tl scintallator-based scanning slot x-ray detector for digital mammography", Proc. SPIE 3336, Medical Imaging 1998: Physics of Medical Imaging, (24 July 1998); https://doi.org/10.1117/12.317062

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