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J. Tokayer, D. Huang; Algorithms to Enhance the Visualization of Macular Blood Vessels in Doppler Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2455. doi: https://doi.org/.
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To improve the visualization of small macular blood vessels using the second-order moving-scatterer-sensitive (MSS) algorithm for Doppler Fourier-domain optical coherence tomography (FD-OCT).
Normal eyes were scanned using the RTVue FD-OCT system (Optovue, Inc. Fremont, CA), which performs 26,000 axial scans per second and has 5-micron depth resolution. Horizontal line scans were taken 1 mm above and below the foveal center. The scan length was 3 mm with a transverse step size of 0.8 microns between adjacent axial scans. Each line scan was completed in 0.15 seconds. We employed both the standard phase-resolved (PR) and the MSS algorithms to detect Doppler shifts in retinal blood vessels.
The transverse scanning motion of the OCT beam introduces an artifactual Doppler shift in the non-flowing retinal tissues (most prominently in the nerve fiber layer and the pigment epithelium) that obscures the small macular vessels in the images (attached) generated by the first-order MSS and PR algorithms. The second order MSS algorithm suppresses the artifactual signal and reveals the flow in multiple macular vessels (image attached).
The MSS algorithm, with the second-order delay line filter, greatly improves the visualization of the small retinal blood vessels close to the fovea. The MSS algorithm requires less transverse scan density compared to the power Doppler algorithm that has also been used to enhance small vessel visualization. The MSS algorithm may provide a practical way to visualize and measure blood flow near the fovea.
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