TY - JOUR
T1 - Validation of two-dimensional and three-dimensional measurements of subpleural alveolar size parameters by optical coherence tomography
AU - Unglert, Carolin I.
AU - Warger, William C.
AU - Hostens, Jeroen
AU - Namati, Eman
AU - Birngruber, Reginald
AU - Bouma, Brett E.
AU - Tearney, Guillermo J.
PY - 2012/1/1
Y1 - 2012/1/1
N2 - 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 micro-computed 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.
AB - 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 micro-computed 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.
UR - http://www.scopus.com/inward/record.url?scp=84878179073&partnerID=8YFLogxK
U2 - 10.1117/1.JBO.17.12.126015
DO - 10.1117/1.JBO.17.12.126015
M3 - Journal articles
C2 - 23235834
AN - SCOPUS:84878179073
SN - 1083-3668
VL - 17
JO - Journal of Biomedical Optics
JF - Journal of Biomedical Optics
IS - 12
M1 - 126015
ER -