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A. Szkulmowska, D. Szlag, M. Szkulmowski, A. Kowalczyk, M. Wojtkowski; Multi-Range Retinal Blood Flow Analysis Using Spectral Oct. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1382. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To reconstruct entire retinal vasculature in three dimensions using Doppler Optical Coherence Tomography.
Ultrahigh resolution (2.5um) Spectral OCT is performed in 6 eyes of 3 healthy volunteers with the aid of laboratory instrument constructed in our group. The velocity of moving blood cells is derived from the Doppler shift (Spectral and Time domain Optical Coherence Tomography - STdOCT) and from phase shifts separately. The velocity value is obtained from 16 A-scans taken in the same location in consecutive moments. The time between these A-scans (the repetition time) determines the velocity range. The dynamic range of velocity measurement remains unchanged, irrespective to the range width. Therefore simple broadening the velocity range allows measuring high flows, however low flows are beyond the velocity measurement. We use multiple measurements with variable velocity window to cover all velocities.
Blood flow velocity measured by OCT depends on blood flow and spatial orientation of blood vessel. The velocity window offered by Doppler OCT methods is not broad enough to detect the entire vasculature of the retina. Velocity maps obtained with widest range revealed flows in choroid and in the biggest vessels in sensory retina, whereas all small vessels are invisible. On the other hand the latter are distinguished and the former are distorted when the velocity range is the smallest. It is possible to broaden velocity range by differentiating the repetition time. Data measured for variable repetition time can be combined enabling reconstruction and segmentation of more complete retinal vasculature. We present three dimensional OCT data of human retina scanned through the vicinity of optic disc and macula. Detailed maps of the flow velocity distribution in these regions will be demonstrated.
We demonstrated that measurement of blood flow velocities performed with a single velocity range determined by constant repetition time is not sufficient to retrieve complete quantitative information about retinal blood flow. We propose to calculate values of blood flow velocities in all retinal vessels using multiple OCT measurements with variable velocity range.
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