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Roman Kuranov, Chad Oian, Gary Noojin, Kurt Schuster, Aurora Shingledecker, David Stolarski, Jeff Oliver; Quantification of local hemoglobin oxygen saturation by 800 nm Dual-Window Spectroscopic OCT. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1500.
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Hemoglobin oxygen saturation (SO2) is an important physiological parameter. Oxygen exchange between blood and tissue occur in blood vessels with diameters below 50 µm. Thus, local SO2 quantification in microvessels is valuable for early diagnostics, therapeutic intervention strategies and investigation laser damage mechanisms. Spectroscopic Optical Coherence Tomography (SOCT) is based on perturbations to OCT spectrum due to the distinct absorption of oxygenated and deoxygenated hemoglobin. Dual window (DW) processing in SOCT was proposed to provide simultaneously high spectral and spatial resolutions. DW SOCT has been shown to provide sufficient sensitivity to quantify microvascular SO2 levels using visible wavelengths where hemoglobin absorption is maximized. However, visible range DW SOCT is far from optimal due to limited imaging depth which is restricted by increased scattering at shorter wavelengths.
SOCT was accomplished with 810 nm super luminescent diode with the DW processing centered at hemoglobin isosbestic wavelength of 798 nm. Phantom vessels with a 50 µm diameter lumen were imaged and SO2 values extracted using a double-pass comparison to adjacent signal that was not passed through the blood. A least-square approximation of the experimental DW OCT spectra utilizing linear combinations of weighted contributions from oxygenated and deoxygenated hemoglobin was implemented.
In this study, we showed the feasibility of SO2 level quantification utilizing DW SOCT with NIR wavelengths (see Figure 1). Even with significantly lower hemoglobin absorption than visible light, achievement of 7% sensitivity in the SO2 range between 60% and 100% was realized in measurement of blood within phantom vessels.
In this study we investigated the feasibility of the dual-window spectroscopic optical coherence tomography (DW SOCT) to provide quantitative hemoglobin oxygen saturation (SO2) levels using infrared light centered at 798 nm wavelength in contrast to previously used visual light. Infrared SOCT has improved imaging depth as compared with visual light SOCT which facilitates clinical applications. Utilizing NIR DW SOCT, we achieved accuracy in SO2 measurements for 50 µm lumen phantom vessels within 7% of clinical standard instrument readings.
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