Ultrahigh Speed OCT Imaging Using Joined Spectral and Time Domain (STd OCT) Method for Enhanced Visualization of Retinal Vessels and Blood Flow Detection

Abstract

Purpose: : Recent advances in spectral / Fourier domain OCT technology enable retinal imaging with speeds an order of magnitude higher than currently available in commercial instruments. Ultrahigh speed imaging allows for development of imaging methods enhancing visualization of retinal structure as well as enabling detection of physiological processes. The purpose of this study is to show enhanced imaging of retinal vascular structure and blood flow detection in retinal vessels with ultrahigh speed OCT instrument (200 000 axial scans/s). We developed a method of joined spectral and time domain OCT method (STd OCT) for simultaneous three dimensional structural and flow-sensitive imaging. We will demonstrate that utilization of this method with specially designed scan protocols allows for optimized imaging of vasculature including vessels in the optic disc and macular region as well as capillary network.

Methods: : Retinal imaging in normal eyes was performed using ultrahigh speed (200 000 axial scans/s) spectral / Fourier domain OCT instrument with a CMOS camera. The imaging resolution was 5 µm axially and 10 µm transversally. Various scan protocols were implemented for investigation of flow in different retinal regions including the macula and optic disk. The total imaging time did not exceed 3s. Data analysis was performed using a method of STd OCT in which detection of spectral fringe pattern and Doppler signal allows for generation of structural and flow images.

Results: : We will show three dimensional imaging of the retinal vasculature in normal eyes. Flow in the region of the optic disc and in the macular region will be calculated and correlated with structural imaging of the vessels in projection OCT fundus images. Enhanced visualization of capillary network will be demonstrated.

Conclusions: : Combination of ultrahigh speed OCT detection and advanced methods of signal analysis such as STd OCT allows for simultaneous imaging of the structure and dynamic processes in the retina. Our investigations show that time and spatially controlled imaging enables imaging of blood flow in different retinal regions and characterized by different velocity projection onto the imaging beam. Visualization of capillary network is also possible. Blood flow detection techniques and vessel structure analysis methods may be important tools in diagnostics of such diseases as diabetic retinopathy or glaucoma.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • image processing