Can a Fourier-based cascaded-systems analysis describe noise in complex shift-variant spatially sampled detectors?

Ian A. Cunningham; Mike Sattarivand; George Hajdok; Jingwu Yao

doi:10.1117/12.534791

6 May 2004 Can a Fourier-based cascaded-systems analysis describe noise in complex shift-variant spatially sampled detectors?

Ian A. Cunningham, Mike Sattarivand, George Hajdok, Jingwu Yao

Author Affiliations +

Proceedings Volume 5368, Medical Imaging 2004: Physics of Medical Imaging; (2004) https://doi.org/10.1117/12.534791
Event: Medical Imaging 2004, 2004, San Diego, California, United States

Abstract

Cascaded-systems analyses have been used successfully by many investigators to describe signal and noise transfer in quantum-based x-ray detectors in medical imaging. However, the Fourier-based linear-systems approach is only valid when assumptions of linearity and shift invariance are satisfied. Digital detectors, in which a bounded image signal is spatially integrated in discrete detector elements, are not shift invariant in their response. In addition, many detectors make use of fiber optics or structured phosphors such as CsI to pass light to a photodetector-both of which have a shift-variant response. These issues raise serious concerns regarding the validity of Fourier-based approaches for describing the signal and noise performance of these detectors. We have used a Monte Carlo approach to compare the image Wiener noise power spectrum (NPS) with that predicted using a Fourier-based approach when these assumptions fail. It is shown that excellent agreement is obtained between Monte Carlo results and those obtained using a Fourier-based wide-sense cyclostationary analysis, including the description of noise aliasing. A simple model of a digital detector coupled to a fiber optic bundle is described using a novel cascaded cyclostationary approach in which image quanta are integrated over fiber elements and then randomly re-distributed at the fiber output. While the image signal sometimes contains significant non-stationary beating artifacts, the Monte Carlo results generally show good agreement with Fourier models of the NPS when noise measurements are made over a sufficiently large region of interest.

Citation Download Citation

Ian A. Cunningham, Mike Sattarivand, George Hajdok, and Jingwu Yao "Can a Fourier-based cascaded-systems analysis describe noise in complex shift-variant spatially sampled detectors?", Proc. SPIE 5368, Medical Imaging 2004: Physics of Medical Imaging, (6 May 2004); https://doi.org/10.1117/12.534791

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