Doppler Optical Coherence Tomography of Retinal Circulation

Abstract

Noncontact retinal blood flow measurements are performed with a Fourier domain optical coherence tomography (OCT) system using a circumpapillary double circular scan (CDCS) that scans around the optic nerve head at 3.40 mm and 3.75 mm diameters. The double concentric circles are performed 6 times consecutively over 2 sec. The CDCS scan is saved with Doppler shift information from which flow can be calculated. The standard clinical protocol calls for 3 CDCS scans made with the OCT beam passing through the superonasal edge of the pupil and 3 CDCS scan through the inferonal pupil. This double-angle protocol ensures that acceptable Doppler angle is obtained on each retinal branch vessel in at least 1 scan. The CDCS scan data, a 3-dimensional volumetric OCT scan of the optic disc scan, and a color photograph of the optic disc are used together to obtain retinal blood flow measurement on an eye. We have developed a blood flow measurement software called "Doppler optical coherence tomography of retinal circulation" (DOCTORC). This semi-automated software is used to measure total retinal blood flow, vessel cross section area, and average blood velocity. The flow of each vessel is calculated from the Doppler shift in the vessel cross-sectional area and the Doppler angle between the vessel and the OCT beam. Total retinal blood flow measurement is summed from the veins around the optic disc. The results obtained at our Doppler OCT reading center showed good reproducibility between graders and methods (<10%). Total retinal blood flow could be useful in the management of glaucoma, other retinal diseases, and retinal diseases. In glaucoma patients, OCT retinal blood flow measurement was highly correlated with visual field loss (R 2 >0.57 with visual field pattern deviation). Doppler OCT is a new method to perform rapid, noncontact, and repeatable measurement of total retinal blood flow using widely available Fourierdomain OCT instrumentation. This new technology may improve the practicality of making these measurements in clinical studies and routine clinical practice. Video LinkThe video component of this article can be found at http://www.jove.com/video/3524/ Protocol 1. Protocol Text 1. Patients are scanned by RTVue Fourier-domain optical coherence tomography (OCT) system (Optovue Inc., Fremont, CA, USA) using the circumpapillary double-circular scan (CDCS) and the 3D optic disc scan. 1. The CDCS pattern consists of two concentric circles around the optic nerve head. The inner ring diameter is 3.40 mm and the outer ring diameter is 3.75 mm. This pattern transects all branch retinal arteries and veins emanating from the optic nerve head. The double circles are performed 6 times in a single scan to cover about 2 cardiac cycles. To calculate Flow velocity, Doppler shift and Doppler will be estimated on vessel detected in the OCT image. (Figure 1a, Figure 1b) 2. A "dual angle" protocol is used to acquire Doppler OCT scans. In the "dual-angle" protocol, 3 scans are obtained with the OCT beam passing through the superona...

Intervisit Repeatability of Retinal Blood Oximetry and Total Retinal Blood Flow Under Varying Systemic Blood Gas Oxygen Saturations

“…From the measured Doppler shift within the vessel and Doppler angle estimation from the vessel center depth difference between two concentric rings, volumetric flow is derived using a semiautomated software (version 2.1.1.4) algorithm named Doppler optical coherence of retinal circulation (DOCTORC). 41,42 The repeatability of TRBF measurements acquired using Doppler SD-OCT was reported in previous publications from our laboratory. 43,44 Metabolic Hyperspectral Retinal Camera (MHRC).…”

Dual-Angle Protocol for Doppler Optical Coherence Tomography to Improve Retinal Blood Flow Measurement

“…[8][9][10] This semi-automated software allows the user to refine the position and boundaries of the automatically detected vessels prior to the calculation of TRBF, vessel cross- sectional area, and average blood flow velocity. As previously described, the flow in each vessel was calculated from the Doppler shift in the vessel crosssectional area and the Doppler angle between the vessel and the OCT beam.…”

“…For this reason, we developed a semiautomated software tool, termed the Doppler OCT of Retinal Circulation (DOCTORC), to allow efficient manual identification and correction of corresponding vessel positions, and subsequent generation of retinal blood flow results. [8][9][10] With high-quality scans, the good reproducibility of this approach has been described in previous publications. [9][10] However, this method has important limitations that reduce the yield of scans with accurate or valid blood flow results.…”

“…[8][9][10] With high-quality scans, the good reproducibility of this approach has been described in previous publications. [9][10] However, this method has important limitations that reduce the yield of scans with accurate or valid blood flow results. One limitation relates to the eye movements that occur during scanning.…”

“…For the dual-angle protocol, 10 the technician first adjusted the OCT scanner so that the laser beam passed through the supranasal edge of the pupil, while keeping the signal strength index (SSI) greater than 40. Three repeated DCSP scans were acquired at this position.…”