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Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation

The index of refraction ([Formula: see text]) of materials and/or tissues depends on their physical properties and serves as a source of optical contrast in imaging. The variations of the index of refraction have also been investigated for diagnostic purposes in various fields, such as hematology, o...

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Autores principales: Photiou, Christos, Pitris, Costas
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Society of Photo-Optical Instrumentation Engineers 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7000875/
https://www.ncbi.nlm.nih.gov/pubmed/31586356
http://dx.doi.org/10.1117/1.JBO.24.10.106001
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author Photiou, Christos
Pitris, Costas
author_facet Photiou, Christos
Pitris, Costas
author_sort Photiou, Christos
collection PubMed
description The index of refraction ([Formula: see text]) of materials and/or tissues depends on their physical properties and serves as a source of optical contrast in imaging. The variations of the index of refraction have also been investigated for diagnostic purposes in various fields, such as hematology, oncology, etc., since they can signify disease and cell dynamic changes. Optical coherence tomography (OCT) has been used in the past to measure the index ex vivo. However, most methodologies described in the literature are not appropriate for in vivo imaging since they require either a mirror below the sample or a complicated imaging setup and algorithms. We describe a technique that uses two images, obtained at different angles, to estimate the index of refraction and can, thus, also be applied in vivo. The index of refraction is calculated from the path-length difference observed by the OCT beam at the two different angles. When a reflector is not available, the path-length difference can be estimated using image registration and the cross-correlation of adjacent A-scans. The proposed technique was validated experimentally using both clear and scattering samples. The resulting values of the index of refraction were within [Formula: see text] of the expected. The main limitation of this technique is the effect of misalignment on the results, requiring the precision provided by an angular-resolved OCT system. These very promising results provide evidence that the dual-angle method should be further investigated and validated on human tissues so that it can be developed into a clinically useful diagnostic tool in the future.
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spelling pubmed-70008752020-02-10 Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation Photiou, Christos Pitris, Costas J Biomed Opt Imaging The index of refraction ([Formula: see text]) of materials and/or tissues depends on their physical properties and serves as a source of optical contrast in imaging. The variations of the index of refraction have also been investigated for diagnostic purposes in various fields, such as hematology, oncology, etc., since they can signify disease and cell dynamic changes. Optical coherence tomography (OCT) has been used in the past to measure the index ex vivo. However, most methodologies described in the literature are not appropriate for in vivo imaging since they require either a mirror below the sample or a complicated imaging setup and algorithms. We describe a technique that uses two images, obtained at different angles, to estimate the index of refraction and can, thus, also be applied in vivo. The index of refraction is calculated from the path-length difference observed by the OCT beam at the two different angles. When a reflector is not available, the path-length difference can be estimated using image registration and the cross-correlation of adjacent A-scans. The proposed technique was validated experimentally using both clear and scattering samples. The resulting values of the index of refraction were within [Formula: see text] of the expected. The main limitation of this technique is the effect of misalignment on the results, requiring the precision provided by an angular-resolved OCT system. These very promising results provide evidence that the dual-angle method should be further investigated and validated on human tissues so that it can be developed into a clinically useful diagnostic tool in the future. Society of Photo-Optical Instrumentation Engineers 2019-10-04 2019-10 /pmc/articles/PMC7000875/ /pubmed/31586356 http://dx.doi.org/10.1117/1.JBO.24.10.106001 Text en © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
spellingShingle Imaging
Photiou, Christos
Pitris, Costas
Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
title Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
title_full Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
title_fullStr Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
title_full_unstemmed Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
title_short Dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
title_sort dual-angle optical coherence tomography for index of refraction estimation using rigid registration and cross-correlation
topic Imaging
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7000875/
https://www.ncbi.nlm.nih.gov/pubmed/31586356
http://dx.doi.org/10.1117/1.JBO.24.10.106001
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