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Li Zhang, Michael David Abramoff, Sebastian M Waldstein, Bianca Gerendas, Ana-Maria Glodan, Christian Simader, Ursula Schmidt-Erfurth, Milan Sonka; Reproducibility of automated choroidal thickness measurements: swept-source OCT and spectral-domain OCT using enhanced depth imaging. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4796.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study was to evaluate the reproducibility of a fully automated three-dimensional method capable of segmenting the entire choroid and quantifying choroidal thicknesses in optical coherence tomography (OCT) image data from two different deep-range imaging techniques, swept-source (SS)-OCT using a 1050nm wavelength and spectral-domain (SD)-OCT using enhanced depth imaging (EDI).
Nine healthy subjects underwent OCT imaging using two different machines from Topcon (DRI OCT-1) (512×256×992 voxels, 6.0×6.0×2.6mm3, voxel size of 11.7×23.4×2.6μm3) and Spectralis (512×97×496 voxels, 5.9×5.9×1.9mm3, voxel size of 11.4×60.9×3.9μm3) using EDI within one hour. Nine independent macula-centered volumetric scans were obtained from each scanner (18 in total). First, a shape-prior based soft-constraint graph-search method was employed to segment Bruch’s membrane (BM), which is modeled as a convex arc on each B-scan. Second, a combined graph-cut-graph-search method was utilized to segment the posterior choroidal surface. Choroidal thickness maps were derived from local distances between the posterior choroidal surface and Bruch’s membrane. To evaluate the test-retest reproducibility between two SD-OCTs, coefficients of variation (CV) of the average choroidal thickness were determined using the root mean square (RMS) approach. Differences of the average choroidal thickness were also reported.
The results showed a high correlation between the two evaluated OCT scanners (R2 = 0.97). The RMS CV was 6.8%. The difference assessment showed an average choroidal thickness bias of 24.7µm (8.1% of the total choroidal thickness) for the two OCT scanners.
We have developed a fully automated three-dimensional method for segmenting the choroidal layer and quantifying choroidal thickness. The method yielded highly robust segmentation results on Topcon SS-OCT and Spectralis SD-OCT scans. Our results have a potential to facilitate multi-center studies with heterogeneous device utilization.
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