Purpose:
To demonstrate the potential of phase variance-based motion contrast imaging using ultrahigh speed Fourier domain OCT (Fd-OCT) for in-vivo visualization of retinal microvasculature without use of extrinsic contrast agents, but yielding structural details comparable to fluorescein angiography.
Methods:
Ultrahigh speed Fd-OCT in vivo human retinal imaging (acquisition speed: 125,000 A-scan/s) was achieved by implementing a CMOS camera (Basler) based OCT system. Each frame consists of 760 A-lines within the B-scan and a flyback time which results in 150 frames/s acquisition speed (6.5 µs exposure time). Different sampling densities and scanning areas were used while the total acquisition time per volume was kept below 5.2 seconds to reduce motion artifacts. The phase variance-based motion contrast technique spatially identifies locations of motion within the retina vasculature. A histogram-based noise analysis of the motion contrast images was used to reduce the motion noise created by transverse eye motion. En face summation images created from the 3D motion contrast data were extracted with segmentation of selected retinal layers to provide non-invasive vascular visualization comparable to currently used invasive angiographic imaging.
Results:
In vivo
Conclusions:
Motion contrast imaging of the retina with the enhanced OCT acquisition speed enables extraction of 2D and 3D retinal vascular flow maps. Reduction of image acquisition time has led to a dramatic decrease of motion artifacts and increased the region of interest that can be imaged with single volume acquisition.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • image processing • retina