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Biomed Opt Express. 2015 Jul 10;6(8):2840-53. doi: 10.1364/BOE.6.002840. eCollection 2015 Aug 1.

Measuring oxygen saturation in retinal and choroidal circulations in rats using visible light optical coherence tomography angiography.

Author information

1
Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd. Evanston, IL 60208 USA ; These authors contributed equally to this work.
2
Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd. Evanston, IL 60208 USA ; Department of Ophthalmology, Northwestern University, 2145 Sheridan Rd., Evanston 60208, USA.

Abstract

Visible light optical coherence tomography (vis-OCT) has demonstrated its capability of measuring vascular oxygen saturation (sO2) in vivo. Enhanced by OCT angiography, the signal from microvasculature can be further isolated and directly used for sO2 extraction. In this work, we extended the theoretical formulation for OCT angiography-based oximetry by incorporating the contribution from motion contrast enhancement. We presented a new method to eliminate the associated confounding variables due to blood flow. First, we performed in vitro experiments to verify our theory, showing a stable spectral derivative within the selected wavelength bands for sO2 extraction. Then, we tested our method in vivo to measure retinal sO2 in rats inhaling different gas mixtures: normal air, 5% CO2, pure O2, and 10% O2. Absolute sO2 values in major arterioles and venules in the retinal circulation can be accurately measured. In addition, we demonstrated the relative changes of sO2 can be measured non-invasively from choriocapillaris immediately underneath the retinal pigmented epithelium (RPE) in rodents.

KEYWORDS:

(110.4500) Optical coherence tomography; (170.1460) Blood gas monitoring; (170.2655) Functional monitoring and imaging; (170.6480) Spectroscopy, speckle

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