Response of CZT pixels to parallel and oblique x rays

R. J. LeClair; E. L. McCarthy

doi:10.1117/12.2549546

16 March 2020 Response of CZT pixels to parallel and oblique x rays

R. J. LeClair, E. L. McCarthy

Proceedings Volume 11312, Medical Imaging 2020: Physics of Medical Imaging; 113123Y (2020) https://doi.org/10.1117/12.2549546
Event: SPIE Medical Imaging, 2020, Houston, Texas, United States

Abstract

CZT detectors are gaining popularity in the medical field. A numerical study of the response of CZT detector pixels to parallel and oblique x rays was conducted. The average k-fluorescence energy generated in a given pixel is 26.0 keV. It is assumed that such x rays travel a mean free path mfp = 0.161 mm in CZT before being absorbed. For applications in nuclear medicine, incident 140 keV photons were used. Each pixel had an area 1.5 mm x 3.3 mm and thickness 5 mm. The spacing between pixels was Δ = 0:3 mm and since Δ >mfp, the model predicts no cross talk between pixels. For parallel photons, the probability of escape is PF_esc = 4:0% and the quantum efficiency η = 0:88. Next consider an isotropic source located at a distance 20 cm from the detector plane. For incident angles of 0° to 23° η varied from 0.88 to 0.5 and the fluorescence escape from 3.8 % to 2.0 %. For breast CT applications a typical pixel size is 0.2 mm by 0.2 mm and thickness 0.75 mm. The corresponding values for photons of energy 60 keV are as follows: (i) parallel η = 0:94, PF_esc = 30%, oblique η = 0:94, PF_esc = 30% at 0°; η = 0:55, PF_esc = 18% at 23°. This work provides some quantification of the response of CZT detector pixels to x rays. Cross talk would need to be examined for the breast CT detector.

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R. J. LeClair and E. L. McCarthy "Response of CZT pixels to parallel and oblique x rays", Proc. SPIE 11312, Medical Imaging 2020: Physics of Medical Imaging, 113123Y (16 March 2020); https://doi.org/10.1117/12.2549546

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KEYWORDS

Sensors

Photons

Luminescence

Quantum efficiency

Chemical species

Breast

Cadmium

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