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Ranjan Rajendram, Felix Fleischhauer, Sophie Caujolle, Michael Maria, Thomas Feuchter, Lasse Leick, Adrian Podoleanu; Localized absorption measurements for possible oxygen saturation using visible-light spectroscopic optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):472.
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© ARVO (1962-2015); The Authors (2016-present)
Spectroscopic optical coherence tomography (SOCT) combines imaging of optical coherence tomography (OCT) with localized absorption, which is used as functional information. By covering the spectral range from 490 to 730 nm a powerful tool to measure localized (de-)oxygenated hemoglobin for oxygen saturation estimation is being developed. This can be used in applications, such as retinal venous and arteriolar occlusions, diabetic retinopathy, glaucoma or assessment of central venous and arteriolar oxygen saturation.
Using a spectrometer based OCT, one has direct access to wavelength information. The measured spectrum is divided in 8 spectral windows, covering unique parts of the spectrum, and the OCT data are processed on each window separately and a cross link between spectral and structural information is obtained.Measurements are done with a 1:1, 1:2, 1:3, 1:10 and 1:100 concentration of Rhodamine B to ethanol, filled in a 50 µm cuvette and its attenuation is measured and compared to literature. Front and back surface of the cuvette are used and their amplitude compared. The attenuation for each window is calculated and used to estimate the absorption of the spectral windows. The OCT signal is attenuated by scattering, absorption and signal decay over imaging depth (roll-off). Rhodamine B is chosen because of its similar absorption peak, around 542 nm, as hemoglobin.
The measurements show that SOCT can be used to reconstruct the absorption maximum of Rhodamine B , but the accuracy degrades with fading concentration (see Fig. 1 and 2). The 1:100 concentration shows false results, which means that we have overcome the sensitivity of our set-up.
We can show that using SOCT can be used to find the absorption maximum of Rhodamine B and the signal degrades with thinner solutions.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Comparison of Rhodamine B absorption spectrum to SOCT measured attenuation using different concentrations. The measurements show that SOCT can be used to reconstruct the absorption maximum of Rhodamine B, but the accuracy degrades with fading concentration. Due to smaller attenuation at 542 nm the peak width appear broader.
Measured attenuation with SOCT for different solutions. A high Rhodamine B concentration results in a higher attenuation in the OCT signal around 542 nm. Attenuation in OCT signal is caused by roll-off, scattering and absorption.
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