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Journal of Biomedical Optics • Open Access

Validation of two-dimensional and three-dimensional measurements of subpleural alveolar size parameters by optical coherence tomography
Author(s): Carolin I. Unglert; William C. Warger; Jeroen Hostens; Eman Namati; Reginald Birngruber; Brett E. Bouma; Guillermo J. Tearney

Paper Abstract

Optical coherence tomography (OCT) has been increasingly used for imaging pulmonary alveoli. Only a few studies, however, have quantified individual alveolar areas, and the validity of alveolar volumes represented within OCT images has not been shown. To validate quantitative measurements of alveoli from OCT images, we compared the cross-sectional area, perimeter, volume, and surface area of matched subpleural alveoli from microcomputed tomography (micro-CT) and OCT images of fixed air-filled swine samples. The relative change in size between different alveoli was extremely well correlated (r<0.9, P<0.0001), but OCT images underestimated absolute sizes compared to micro-CT by 27% (area), 7% (perimeter), 46% (volume), and 25% (surface area) on average. We hypothesized that the differences resulted from refraction at the tissue-air interfaces and developed a ray-tracing model that approximates the reconstructed alveolar size within OCT images. Using this model and OCT measurements of the refractive index for lung tissue (1.41 for fresh, 1.53 for fixed), we derived equations to obtain absolute size measurements of superellipse and circular alveoli with the use of predictive correction factors. These methods and results should enable the quantification of alveolar sizes from OCT images in vivo.

Paper Details

Date Published: 12 December 2012
PDF: 11 pages
J. Biomed. Opt. 17(12) 126015 doi: 10.1117/1.JBO.17.12.126015
Published in: Journal of Biomedical Optics Volume 17, Issue 12
Show Author Affiliations
Carolin I. Unglert, Wellman Ctr. for Photomedicine (United States)
William C. Warger, Wellman Ctr. for Photomedicine (United States)
Jeroen Hostens, Bruker microCT (Belgium)
Eman Namati, Wellman Ctr. for Photomedicine (United States)
Reginald Birngruber, Univ. zu Lübeck (Germany)
Brett E. Bouma, Wellman Ctr. for Photomedicine (United States)
Guillermo J. Tearney, Wellman Ctr. for Photomedicine (United States)

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