Effect of direct x-ray interaction in the photodetector on image noise for a CCD/scintillator system

Michael J. Flynn; Sean M. Hames; James J. Ciarelli

doi:10.1117/12.237775

11 April 1996 Effect of direct x-ray interaction in the photodetector on image noise for a CCD/scintillator system

Michael J. Flynn, Sean M. Hames, James J. Ciarelli

Proceedings Volume 2708, Medical Imaging 1996: Physics of Medical Imaging; (1996) https://doi.org/10.1117/12.237775
Event: Medical Imaging 1996, 1996, Newport Beach, CA, United States

Abstract

Digital x-ray imaging detectors for soft x-rays (1 to 50 keV) are significant for medical mammography, dental radiography, microradiography, x-ray diffraction, and x-ray telescope applications. For systems in which a scintillator is optically coupled to a photodetector, a small number of electrons are produced for each interaction in the scintillator (more than 10 e^- in well designed systems). However, x-rays interacting directly in the photodetector produce a large charge for each detected event (about 4,700 e^- for a 17 keV x-ray absorbed in silicon. These direct interactions can significantly increase image noise even when their interaction probability and contribution to image signal are low. In this paper we report on analytic investigations of the direct and indirect contributions to noise for a system consisting of a CsI scintillator, fiber optic coupler, and CCD photo-detector. The fiber optic coupler is shown to be essential to shield the CCD detector from direct interactions. A 3 mm thick fiber optic coupler is sufficient to eliminate most of the events that can noticeably increase noise.

Citation Download Citation

Michael J. Flynn, Sean M. Hames, and James J. Ciarelli "Effect of direct x-ray interaction in the photodetector on image noise for a CCD/scintillator system", Proc. SPIE 2708, Medical Imaging 1996: Physics of Medical Imaging, (11 April 1996); https://doi.org/10.1117/12.237775

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