Abstract
The variability in the spatial orientation of retinal blood vessels near the optic nerve head (ONH) results in imprecision of the measured Doppler angle and therefore the pulsatile blood flow (BF), when those parameters are evaluated using Doppler OCT imaging protocols based on dual-concentric circular scans. Here, we utilized a dense concentric circle scanning protocol and evaluated its precision for measuring pulsatile retinal BF in rats for different numbers of the circular scans. An spectral domain optical coherence tomography (SD-OCT) system operating in the 1060-nm spectral range with image acquisition rate of 47,000 A-scans/s was used to acquire concentric circular scans centered at the rat's ONH, with diameters ranging from 0.8 to 1.0mm. A custom, automatic blood vessel segmentation algorithm was used to track the spatial orientation of the retinal blood vessels in three dimensions, evaluate the spatially dependent Doppler angle and calculate more accurately the axial BF for each major retinal blood vessel. Metrics such as retinal BF, pulsatility index, and resistance index were evaluated for each and all of the major retinal blood vessels. The performance of the proposed dense concentric circle scanning protocols was compared with that of the dual-circle scanning protocol. Results showed a 3.8±2.2 deg difference in the Doppler angle calculation between the two approaches, which resulted in ∼7% difference in the calculated retinal BF.
Highlights
Pulsatile retinal blood flow (BF) is associated with a number of ocular vascular-related diseases, such as diabetic retinopathy,[1] central retinal venous occlusion,[2] age-related macular degeneration,[3] and glaucoma.[4]
Recent studies[1,2,3,4] indicated that metrics that characterize the pulsatility of retinal BF are sensitive to early pathophysiological changes in the retina, accurate assessment of retinal BF pulsatility can aid the early diagnosis of potentially blinding diseases
Doppler optical coherence tomography (DOCT) offers higher sensitivity and provides simultaneously both structural and BF/blood perfusion information about the imaged object, which offers an opportunity to examine the relationship between morphological and BF changes in the retina induced by retinal diseases.[8]
Summary
Pulsatile retinal blood flow (BF) is associated with a number of ocular vascular-related diseases, such as diabetic retinopathy,[1] central retinal venous occlusion,[2] age-related macular degeneration,[3] and glaucoma.[4]. An alternative approach to measuring absolute retinal BF with DOCT is to utilize a dual-circle scanning pattern[6] and use the location displacement of blood vessels between the two circular OCT scans to calculate the Doppler angle.
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