Abstract
Purpose :
Visualization of vasculature from OCTA is typically done by generating en face angiography images between boundaries of interest segmented from the structural OCT data. The purpose of this study is to qualitatively and quantitatively evaluate a new multilayer segmentation algorithm in comparison to a commercial implementation that segments only the retinal pigment epithelium (RPE) and inner limiting membrane (ILM), and estimates the remaining layers based on predetermined rules.
Methods :
One eye from each of 34 subjects with early diabetic retinopathy were imaged on a CIRRUS™ HD-OCT 5000 with AngioPlex® OCT Angiography (ZEISS, Dublin, CA) with the 3x3 OCT Angio scan. The commercial segmentation defines the superficial retinal layer (SRL) is as the layer between the ILM (ZILM) and an approximation of the inner plexiform layer, ZIPL=ZILM+70%*(TILM-OPL), where TILM-OPL is the thickness between ILM and the outer plexiform layer (OPL), which is estimated as ZOPL=ZRPEfit – 110 μm. The deep retinal layer (DRL) is defined as being between the IPL and OPL. For the multilayer method, the SRL is defined as being between the segmented ILM and the segmented outer boundary of the IPL minus 10 microns, while the DRL is defined as being between the segmented IPL minus 10 microns and the segmented outer boundary of the inner nuclear layer (INL) plus 30 microns. The density of vasculature in these angiography en face images was quantified using the commercial method to estimate the percent area of perfused vasculature (Perfusion Density). The quantitative results were compared using linear regression. The images were also reviewed qualitatively to determine which provided a visualization of the vasculature most consistent with the expected anatomy.
Results :
Multilayer segmentation qualitatively had better vessel continuity and visualization of the deep capillary plexus especially in the parafoveal region (See Figure 1). Regression analysis found the two methods were well correlated, with an r-squared of 0.90 for the SRL (slope of 1.09, offset of 0.05) and 0.89 for the DRL (slope of 1.1, offset of 0.01).
Conclusions :
Multilayer segmentation can allow layers to be created based on the expected structural location, and improves visibility of microvasculature in the deeper retinal layers. Quantitatively the results are similar to the commercial method.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.