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Proceedings Paper

Local noise reduction for emphysema scoring in low-dose CT images
Author(s): Arnold Schilham; Mathias Prokop; Hester Gietema; Bram van Ginneken
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Paper Abstract

Computed Tomography (CT) has become the new reference standard for quantification of emphysema. The most popular measure for emphysema derived from CT is the Pixel Index (PI), which expresses the fraction of the lung volume with abnormally low intensity values. As PI is calculated from a single, fixed threshold on intensity, this measure is strongly influenced by noise. This effect shows up clearly when comparing the PI score for a high-dose scan to the PI score for a low-dose (i.e. noisy) scan of the same subject. This paper presents a class of noise filters that make use of a local noise estimate to specify the filtering strength: Local Noise Variance Weighted Averaging (LNVWA). The performance of the filter is assessed by comparing high-dose and low-dose PI scores for 11 subjects. LNVWA improves the reproducibility of high-dose PI scores: For an emphysema threshold of -910 HU, the root-mean-square difference in PI score drops from 10% of the lung volume to 3.3% of the lung volume if LNVWA is used.

Paper Details

Date Published: 29 April 2005
PDF: 9 pages
Proc. SPIE 5747, Medical Imaging 2005: Image Processing, (29 April 2005); doi: 10.1117/12.595774
Show Author Affiliations
Arnold Schilham, Univ. Medical Ctr. Utrecht (Netherlands)
Mathias Prokop, Univ. Medical Ctr. Utrecht (Netherlands)
Hester Gietema, Univ. Medical Ctr. Utrecht (Netherlands)
Bram van Ginneken, Univ. Medical Ctr. Utrecht (Netherlands)

Published in SPIE Proceedings Vol. 5747:
Medical Imaging 2005: Image Processing
J. Michael Fitzpatrick; Joseph M. Reinhardt, Editor(s)

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