Automatic retinal blood flow calculation using spectral domain optical coherence tomography

Abstract

Optical Doppler tomography (ODT) is a branch of optical coherence tomography (OCT) that can measure the speed of a blood flow by measuring the Doppler shift impinged on the probing sample light by the moving blood cells. However, the measured speed of blood flow is a function of the Doppler angle, which needs to be determined in order to calculate the absolute velocity of the blood flow inside a vessel. We developed a technique that can extract the Doppler angle from the 3D data measured with spectral-domain OCT, which needs to extract the lateral and depth coordinates of a vessel in each measured ODT and OCT image. The lateral coordinates and the diameter of a blood vessel were first extracted in each OCT structural image by using the technique of blood vessel shadowgram, a technique first developed by us for enhancing the retinal blood vessel contrast in the en face view of the 3D OCT. The depth coordinate of a vessel was then determined by using a circular averaging filter moving in the depth direction along the axis passing through the vessel center in the ODT image. The Doppler angle was then calculated from the extracted coordinates of the blood vessel. The technique was applied in blood flow measurements in retinal blood vessels, which has potential impact on the study and diagnosis of blinding diseases like glaucoma.

3-D segmentation of retinal blood vessels in spectral-domain OCT volumes of the optic nerve head

“…The retinal blood vessel locations in 3-D were previously identified using optical Doppler tomography (ODT) images as being located right above vessel shadows in the OCT volumes. 13 Based on this a priori knowledge, the z-positions of the retinal blood vessels approximately corresponded to 3 middle voxels between surfaces 1 and 2 in the isotropic OCT volume. Initial 3-D retinal blood vessels were detected by finding the intersection regions of the 2-D vessel segmentation and the approximate z-positions of the vessels (Fig.…”

Microfluidics analysis of blood using joint spectral and time domain optical coherence tomography

“…The most widely used techniques include the phase resolved Doppler OCT methods [5][6][7][8][9][10][11] and resonant Doppler OCT methods [12,13]. Our group proposed an alternative way of detecting the flow based on the Doppler frequency shift, called joint Spectral and Time domain OCT [14].…”

Blood flow measurement and slow flow detection in retinal vessels with joint spectral and time domain method in ultrahigh-speed OCT

“…Several OCT techniques enabling flow detection in the eye have been introduced up to date. The most widely used include the phase resolved / phase sensitive methods [1][2][3][4][5][6][7], techniques employing Doppler effect [8,9] and resonant Doppler methods [10,11]. Recently our group has introduced a Joint Spectral and Time domain OCT method (STdOCT) which can detect the flow based on the Doppler frequency shift visible in the OCT data as intensity beating signal [12].…”