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

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.

OCT angiography and visible-light OCT in diabetic retinopathy

“…The procedure for retinal oximetry and blood flow measurements with vis-OCT has been demonstrated and validated in rodent models (Chen, Yi & Zhang, 2015, Soetikno, et al, 2015, Yi, et al, 2015b, Yi et al, 2013). The MRO 2 of the inner retina was measured using vis-OCT during progressive systemic hypoxic challenge, where the inhaled oxygen content was progressively decreased (Yi et al, 2013).…”

Dual-band optical coherence tomography using a single supercontinuum laser source

“…Meanwhile, calculating intragroup decorrelation on complex OCT B-scans yielded OCT angiography. 19 The detailed steps to perform spectroscopic OCT analysis for sO 2 were previously documented. 12 Briefly, we adopted shorttime Fourier transform (STFT), which split the entire spectrum into equally spaced narrow bands in k-space.…”

Angiographic and structural imaging using high axial resolution fiber-based visible-light OCT

“…Although vis-OCT penetration is less than conventional OCT in the near infrared band, the choriocapillaris could still be detected. The field of view of angiography images was larger than previous reports of visible-light OCTA [30,60,61]. When imaging chicken embryo, the microvascular and a venous bifurcation were investigated and a laminar behavior was observed near a venous bifurcation.…”