Abstract
Purpose:
To visualize blood flow profiles and alterations in blood flow profiles in vivo in retinal vessels and venous junctions using Doppler FD-OCT and to further gain insight into hemodynamics and study the flow characteristics of the non-Newtonian fluid blood.
Methods:
The blood flow data was acquired by means of a Doppler OCT system with a center wavelength of 840 nm and an A-scan rate of 40 kHz. Flow profiles were automatically measured at certain equidistant positions around venous bifurcations. To do so, 60 B-scans (to allow for averaging) - each consisting of 1000 lines - were recorded at each position. For post-processing, Matlab software was developed which semiautomatically registered and averaged the B-scans. To gain insight in shape alterations of the profiles, different fits, parabolic and non-parabolic ones - for instance 1-(a*r/R)^b - were applied and analyzed.
Results:
Before venous junctions two single, almost parabolic profiles can be seen. Shortly after the junction two pronounced peaks are seen within one profile. With increasing distance from the confluence, an obviously turbulent section follows where we see a non-parabolic, plow shaped profile. With further increasing distance from the confluence a single, almost parabolic peak reoccurs, indicating that the flow is laminar again.
Conclusions:
The ability to measure blood flow profiles in vivo in retinal vessels via Doppler OCT was proved. By qualitative analysis of blood flow profiles, insight into the hemodynamics at vessel diameters as small as 150 µm to 30 µm was gained. A future application of flow profile analysis may be the early detection of onsetting retinal vascular occlusions.
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
688 retina •
436 blood supply