Automated Quantification of Nonperfusion in Three Retinal Plexuses Using Projection-Resolved Optical Coherence Tomography Angiography in Diabetic Retinopathy

Abstract

PurposeThe purpose of this study was to evaluate an automated algorithm for detecting avascular area (AA) in optical coherence tomography angiograms (OCTAs) separated into three individual plexuses using a projection-resolved technique.MethodsA 3 × 3 mm macular OCTA was obtained in 13 healthy and 13 mild nonproliferative diabetic retinopathy (NPDR) participants. A projection-resolved algorithm segmented OCTA into three vascular plexuses: superficial, intermediate, and deep. An automated algorithm detected AA in each of the three plexuses that were segmented and in the combined inner-retinal angiograms. We assessed the diagnostic accuracy of extrafoveal and total AA using segmented and combined angiograms, the agreement between automated and manual detection of AA, and the within-visit repeatability.ResultsThe sum of extrafoveal AA from the segmented angiograms was larger in the NPDR group by 0.17 mm2 (P < 0.001) and detected NPDR with 94.6% sensitivity (area under the receiver operating characteristic curve [AROC] = 0.99). In the combined inner-retinal angiograms, the extrafoveal AA was larger in the NPDR group by 0.01 mm2 (P = 0.168) and detected NPDR with 26.9% sensitivity (AROC = 0.62). The total AA, inclusive of the foveal avascular zone, in the segmented and combined angiograms, detected NPDR with 23.1% and 7.7% sensitivity, respectively. The agreement between the manual and automated detection of AA had a Jaccard index of >0.8. The pooled SDs of AA were small compared with the difference in mean for control and NPDR groups.ConclusionsAn algorithm to detect AA in OCTA separated into three individual plexuses using a projection-resolved algorithm accurately distinguishes mild NPDR from control eyes. Automatically detected AA agrees with manual delineation and is highly repeatable.

Automated boundary detection of the optic disc and layer segmentation of the peripapillary retina in volumetric structural and angiographic optical coherence tomography

“…7(A)-7(C)), the algorithm was able to identify the BMO. Angiograms of the peripapillary retina demonstrated incongruent areas of nonperfusion in the three plexuses (arrows in Figs. 7(E)-7(G)), consistent with our finding in macular scans in DR [6]. In a case of PDR, retinal neovascularization could be clearly identified as flow signal in the vitreous slab (Fig.…”

“…The en face projection of the maximum decorrelation based on anatomic tissue slabs produces angiograms which are similar to traditional angiography [5]. We have presented en face angiograms that show the individual layers of the retinal capillary plexuses [6]. The ability of this technique to observe individual capillary networks may enable earlier detection of microvasculopathies.…”

OCT angiography and visible-light OCT in diabetic retinopathy

“…Automated algorithms quantifying DMI from full retinal thickness angiograms have shown the ability to distinguish DR from healthy controls (Hwang et al, 2016a), as well as trends of avascular area increasing with disease severity (Schottenhamml et al, 2016). Demonstrating the usefulness of OCTA in segmenting the individual capillary plexuses, studies showed that grading DMI in the three distinct plexuses (SCP, MCP, and DCP) had a higher sensitivity and specificity for determining DR versus healthy controls, as well as determining DR stage, compared to grading full retinal thickness angiograms (Zhang et al, 2016b, Hwang et al, 2016b). These results are likely due to the projection artifacts present in the full thickness angiograms, which can occlude the full extent of non-perfusion.…”

Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

“…This is very critical for the development of following automatic quantification softwares, such as CNV detection [5] and nonperfusion area detection on three plexuses [17]. Similar to prior PR method, this new rbPR method also resolves the projection artifacts on a voxel-by-voxel basis.…”

“…PR-OCTA discriminate three distinct retinal plexuses. In diabetic retinopathy, vascular abnormalities have been detected within each individual plexuses with PR-OCTA, findings not possible with conventional OCTA [16,17].…”