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R.A. Leitgeb, E. Götzinger, M. Pircher, C.K. Hitzenberger; Comparing Spectroscopic and Polarization Sensitive Fourier Domain Optical Coherence Tomography for Retinal Imaging . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5661.
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© ARVO (1962-2015); The Authors (2016-present)
To compare spectroscopic and polarization sensitive FDOCT for their ability to visualize spectroscopic, scattering, and micro–structural properties of retinal tissue to enhance OCT image contrast.
FDOCT systems record spectral interference patterns, that yield after Fourier transform the depth resolved sample structures. For large spectral bandwidths it is possible to split the spectrum into two regions centered at different wavelengths, and to calculate the sample structure for each individual spectral band. After subtraction of the two images one is left with a differential image that reflects qualitatively the spectroscopic properties of the sample structure. The tomograms are recorded with a high resolution polarization sensitive frequency domain OCT (PS–FDOCT) system. It is therefore possible to directly compare the polarization characteristics of the retinal tissue with its differential spectroscopic properties.
Polarization sensitive OCT yields information about the tissue birefringence. Tomograms of the polarization properties in the foveal region typically produce a homogenous impression for the different retinal layers except for the retinal pigment epithelium. This layer causes loss of polarization which clearly contrasts the retinal pigment epithelium (RPE) in the tomograms against the neighboring retinal structures. The differential spectroscopy approach was applied to measured FDOCT data of a healthy human retina. The resulting image yields as well a clear distinct signal for the RPE. Hence it can be used like polarization sensitive imaging for enhancing the tissue contrast.
The differential spectroscopic analysis of retinal tissue shows as well as polarization sensitive FDOCT a contrasted signal for the RPE. Such distinction becomes especially important for the interpretation of tomograms of pathologic retinas. The visible change in the spectroscopic as well as polarization properties of the RPE is believed to be due to the enhanced light scattering at the pigment cells. The advantage of the spectroscopic analysis is its simplicity since it can be applied in a post processing step to data obtained with any broadband FDOCT system without the need of two orthogonal polarization channels.
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