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Proceedings Paper

Noise characterization of computed tomography using the covariance matrix
Author(s): Claudia C. Brunner; Stefanie A. Hurowitz; Samir F. Abboud; Christoph Hoeschen; Iacovos S. Kyprianou
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Paper Abstract

In order to compare different imaging systems, it is necessary to obtain detailed information about the system noise, its deterministic properties and task specic signal-to-noise ratio (SNR). The current standard method for characterizing noise in CT scanners is based on the pixel standard deviation of the image of a water-equivalent uniform phantom. The Fourier-based noise power spectrum (NPS)improves on the limitations of the pixel standard deviation by accounting for noise correlations. However, it has been shown that the Fourier-methods used to describe the system performance result in systematic errors as they make some limiting assumptions such as shift invariance and wide sense stationarity, which are not satised by real CT systems. For a more general characterization of the imaging system noise, a covariance matrix eigenanalysis can be performed. In this paper we present the experimental methodology for the evaluation of the noise of computed tomography systems. We used a bench-top at-panel-based cone-beam CT scanner and a cylindrical water-lled PMMA phantom. For the 3-dimensional reconstructed volume, we calculated the covariance matrix, its eigenvectors and eigenvalues for the xy-plane as well as for the yz-plane, and compared the results with the NPS. Furthermore, we analyzed the location-specic noise in the images. The evaluation of the noise is a rst step toward determining the task-specic SNR.

Paper Details

Date Published: 23 March 2010
PDF: 10 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76224Z (23 March 2010); doi: 10.1117/12.845494
Show Author Affiliations
Claudia C. Brunner, Technischen Univ. München Hospital rechts der Isar (Germany)
Helmholtz Zentrum München GmbH (Germany)
Stefanie A. Hurowitz, U.S. Food and Drug Administration (United States)
Samir F. Abboud, U.S. Food and Drug Administration (United States)
Christoph Hoeschen, Helmholtz Zentrum München GmbH (Germany)
Iacovos S. Kyprianou, U.S. Food and Drug Administration (United States)

Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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