Purpose:
To demonstrate the performance of a dual-beam Doppler optical coherence tomography system to visualize the microvasculature within the human retina.
Methods:
The sample arm beams from two identical spectral domain optical coherence tomography (SD-OCT) systems are combined such that there is a small horizontal offset between them at the retina. Thereby we record two tomograms which are slightly separated in time. This approach allows us to delay the time between the two necessary phase measurements arbitrarily without the need to adjust the acquisition time. Phase-resolved Doppler analysis is performed between these two datasets, which, together with the inherently present intensity images, allows us to extract a 3D map of the vascular and microvascular network within the human retina in vivo. The horizontal displacement between both sample beams was adjusted such that the time difference between the two phase measurements was 2.5 ms. With these measurement settings we calculated a minimum resolvable flow speed of approximately 10.3 µm/s. Because the maximum detectable flow speed is not limited by the 2π phase ambiguity our system shows a high dynamic range.
Results:
Measurements on healthy human volunteers were performed and the extracted 3D vessel maps are displayed as en face projections. The appended figure shows an image which is stitched together from several measurements ranging from the optic disk towards the fovea.
Conclusions:
In conclusion we demonstrated a dual-beam phase-resolved Doppler optical coherence tomography system which is capable of visualizing not only the major vessels but also the microvasculature within the human retina in vivo.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)