![]() The superficial inner retina segmentation (Figure 2A) shows vasculature in the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL). #AARONS CUBE SIGNAL PATH SOFTWARE#The AngioVue software can be used to manually segment OCT angiograms into en face projections of the superficial, intermediate, and deep inner retinal vascular plexuses, outer retina, and choriocapillaris. This results in a tradeoff between image resolution and field of view, with 2.0 x 2.0 mm OCTA images having the highest resolution and the best microvascular detail, but 8.0 x 8.0 mm OCTA images having the largest field of view. 6 The same scanning density can be used to create a variety of OCTA image sizes: 2.0 x 2.0 mm, 3.0 x 3.0 mm, 6.0 x 6.0 mm, or 8.0 x 8.0 mm (Figure 1). The device scans at 70 000 a-scans per second and obtains OCTA images of 304 x 304 a-scans in approximately 3.0 seconds, comparing two OCT b-scans at each given cross-section. Currently, prototype software (AngioVue, OptoVue) is under limited clinical testing across the United States on the commercially available RTVue XR Avanti spectral-domain OCT (SD-OCT) device (OptoVue). Slow scanning speeds result in an unacceptable tradeoff between limited field of view, increased image acquisition time, and decreased image resolution. In order to obtain a densely sampled volume, OCTA requires higher imaging speeds than most currently available OCT machines provide. This image shows 2.0 x 2.0 mm (A), 3.0 x 3.0 mm (B), 6.0 x 6.0 mm (C), and 8.0 x 8.0 mm (D) images at the fovea, and 3.0 x 3.0 mm (E) and 6.0 x 6.0 mm (F) images at the optic nerve. OCTA centered at the fovea and the optic nerve in an eye with no known disease. The axial resolutions of the corresponding OCT b-scans are similar to the resolution of individual b-scans within a standard volumetric cube scan.įigure 1. Therefore, by scrolling through the OCT angiogram in a similar way as one might with a standard OCT cube scan, blood flow and structural information can be evaluated in tandem. 1-5 The OCTA technology coregisters the en face angiographic maps (OCT angiograms) with the corresponding cross-sectional OCT b-scans. Once axial bulk motion due to patient movement between sequential OCT b-scans is factored out, differences between repeated OCT b-scans are assumed to represent erythrocyte movement and, therefore, blood flow. The device compares the differences in the backscattered OCT signal intensity between sequential OCT b-scans obtained at a given cross-section (decorrelation signal) and uses this information to create a depth-resolved, en face map of the retinal and choroidal blood flow. OCTA works by creating a decorrelation signal. There is also potential for using it to visualize abnormal blood flow in patients with ophthalmic diseases such as neovascular age-related macular degeneration (AMD), diabetic retinopathy (DR), and retinal vascular disease. ![]() Initial clinical experience with OCTA has been promising, suggesting that OCTA can provide fine microvascular detail at least equivalent to that of fluorescein angiography (FA). Optical coherence tomography angiography (OCTA) is an emerging imaging technique that employs motion contrast extracted from high-speed OCT images to generate high-resolution en face angiographic images noninvasively, rapidly, and without a dye injection. OCTA could someday be used for monitoring CNV, DR, vascular occlusive disease, and macular telangiectasia.Software for OCTA is undergoing clinical testing on SD-OCT devices.OCTA calculates differences in OCT b-scans to indicate erythrocyte movement. ![]()
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