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Proceedings Paper

Effect of finite detector-element width on the spatial-frequency-dependent detective quantum efficiency
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Paper Abstract

Image blur in digital imaging systems results from both the spatial spreading of quanta representing the image in the detector system and from the integration of quanta over the finite detector element width. Linear-systems theory has often been used to describe these blurring mechanisms as a convolution, implying the existence of a corresponding modulation transfer function (MTF) in the spatial-frequency domain. This also implies that the resulting noise- power spectrum (NPS) is modified by the square of the blurring MTF. This deterministic approach correctly describes the effect of each blurring mechanism on the overall system MTF, but does not correctly describe image noise characteristics. This is because the convolution is a deterministic calculation, and neglects the statistical properties of the image quanta. Rabbani et al. developed an expression for the NPS following a stochastic spreading mechanism that correctly accounts for these statistical properties. Use of their results requires a modification in how we should interpret the convolution theorem. We suggest the use of a `stochastic' convolution operator, that uses the Rabbani equation for the NPS rather than the deterministic result. This approach unifies the description of both image blur and image noise into a single linear-systems framework. This method is then used to develop expressions for the signal, NPS, DQE, and pixel SNR for a hypothetical digital detector design that includes the effects of conversion to secondary quanta, stochastic spreading of the secondary quanta, and a finite detector-element width.

Paper Details

Date Published: 8 May 1995
PDF: 9 pages
Proc. SPIE 2432, Medical Imaging 1995: Physics of Medical Imaging, (8 May 1995); doi: 10.1117/12.208331
Show Author Affiliations
Ian A. Cunningham, John P. Robarts Research Institute and Victoria Hospital (Canada)
Michael S. Westmore, John P. Robarts Research Institute and Victoria Hospital (Canada)
Aaron Fenster, John P. Robarts Research Institute and Victoria Hospital (Canada)

Published in SPIE Proceedings Vol. 2432:
Medical Imaging 1995: Physics of Medical Imaging
Richard L. Van Metter; Jacob Beutel, Editor(s)

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