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B.A. Bower, J.A. Izatt; Measurement of Retinal Vessel Autoregulation in Response to Increased Blood–Oxygen Concentration with Spectral Domain Doppler Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4042.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the application of Spectral Domain Doppler Optical Coherence Tomography (SDOCT) to the measurement of changes in retinal vessel thickness and blood flow in response to increased blood oxygenation.
A high–speed SDOCT image system was created using a low–cost superluminescent diode source (841 nm center wavelength and 49 nm bandwidth) and a custom spectrometer. The patient interface is a standard slit–lamp biomicroscope with a 60 Ø Volk lens. Custom software acquired, resampled from wavelength to wavenumber, Fourier transformed, processed, and displayed [512 (axial) pixel x 1000 (lateral) line] volumetric and time–sequential images at 17 fps and [512 pixel x 500 line] Doppler images at 5.8 fps. Medical–grade, 100% oxygen was supplied to the subject at a rate of 6 L/min through a non–rebreather mask. 100 line (azimuth) x 100 line (elevation) volumes were acquired and the summed–voxel projection computed at 2 frames per second for fast OCT fundus alignment. Two vessels in the superior arcade were selected using the OCT fundus image and flow through these vessels was measured using Doppler SDOCT. Data was acquired before oxygen inhalation, just after 5 a minute interval of oxygen intake, and 5 minutes post the cessation of oxygen inhalation. Doppler images approximately following systole were analyzed.
Vessel diameters were calculated as the zero–crossings of parabolic fits to the flow frequency signal from the selected vessels. Peak Doppler frequency was calculated as the maximum to the parabolic fit (Fig. 1). In preliminary data, we detected a constriction of vessel diameter under constant oxygen inhalation of 7% and a reduction in flow frequency of 38%. This is in good agreement with both theory and previous results from laser Doppler velocimetry studies.
Doppler SDOCT has been used to measure the autoregulatory response of human retinal vessels in–vivo. High–speed retinal SDOCT can be used to investigate functional changes in the retinal vasculature due to improved phase stability and reduced motion artifact.
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