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Christoph K Hitzenberger, Andreas Wartak, Florian Beer, Bernhard Baumann, Michael Pircher; Blood flow quantification in retinal vessels by three-channel Doppler OCT with variable beam switching patterns. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5863.
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To demonstrate the capability of a new three-channel Doppler OCT system to measure absolute blood flow in retinal vessels with a wide range of blood velocities.
A new three-channel swept source Doppler OCT system (center wavelength 1045 nm, sweep speed 100 kHz) was developed and used to measure blood flow in retinal vessels. The three sampling beams illuminate the retina at different angles (equilateral pyramid beam geometry), providing access to three independent components of the velocity vector of blood cells moving in a vessel. To extend imaging depth and sensitivity, as compared to our previously reported instruments, a time encoding of beams by use of sequential switching was used. To accommodate a wide range of blood velocities, variable switching schemes were used to adapt the time delay between A-scans from which the velocity information (phase delay) was derived. Inter A-scan switching provided a time delay of 33 µs between related A-scans, best suited for slower blood flow, while intra A-scan switching provided a time delay of 10 µs, suitable for imaging fast blood flow.The use of the new system was demonstrated by resolving blood flow variations in individual arteries of healthy subjects during the heart beat cycle.
Fig. 1 shows color coded images of blood flow recorded in a single artery of a healthy human eye. High flow velocity is observed during the systolic phase. The image series recorded with inter A-scan switching (g) shows good velocity resolution during the diastolic phase, however, phase wraps (color oscillations) during the systolic phase prevent a quantitative flow measurement. The intra A-scan switching pattern (h) does not show phase wrapping artifacts, enabling direct quantitative flow measurements also in the systolic phase.
Three channel Doppler OCT with variable switching patterns can be used to quantify blood flow velocity in a wide range of flow velocity situations.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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