Normalization of CT scans reconstructed with different kernels to reduce variability in emphysema measurements

L. Gallardo Estrella; B. van Ginneken; E. M. van Rikxoort

doi:10.1117/12.2007962

18 March 2013 Normalization of CT scans reconstructed with different kernels to reduce variability in emphysema measurements

L. Gallardo Estrella, B. van Ginneken, E. M. van Rikxoort

Author Affiliations +

Proceedings Volume 8670, Medical Imaging 2013: Computer-Aided Diagnosis; 86700E (2013) https://doi.org/10.1117/12.2007962
Event: SPIE Medical Imaging, 2013, Lake Buena Vista (Orlando Area), Florida, United States

Abstract

Chronic Obstructive Pulmonary Disease (COPD) is a lung disease characterized by progressive air flow limitation caused by emphysema and chronic bronchitis. Emphysema is quantified from chest computed tomography (CT) scans as the percentage of attentuation values below a fixed threshold. The emphysema quantification varies substantially between scans reconstructed with different kernels, limiting the possibilities to compare emphysema quantifications obtained from scans with different reconstruction parameters. In this paper we propose a method to normalize scans reconstructed with different kernels to have the same characteristics as scans reconstructed with a reference kernel and investigate if this normalization reduces the variability in emphysema quantification. The proposed normalization splits a CT scan into different frequency bands based on hierarchical unsharp masking. Normalization is performed by changing the energy in each frequency band to the average energy in each band in the reference kernel. A database of 15 subjects with COPD was constructed for this study. All subjects were scanned at total lung capacity and the scans were reconstructed with four different reconstruction kernels. The normalization was applied to all scans. Emphysema quantification was performed before and after normalization. It is shown that the emphysema score varies substantially before normalization but the variation diminishes after normalization.

Citation Download Citation

L. Gallardo Estrella, B. van Ginneken, and E. M. van Rikxoort "Normalization of CT scans reconstructed with different kernels to reduce variability in emphysema measurements", Proc. SPIE 8670, Medical Imaging 2013: Computer-Aided Diagnosis, 86700E (18 March 2013); https://doi.org/10.1117/12.2007962

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