Evaluation of Deep Learning-Based OCTA Denoising in Retinal Vessel Assessment

To evaluate the performance of the N2V2 denoising algorithm on optical coherence tomography angiography (OCTA) retinal vasculature quantification.

OCTA scans (3 × 3, 6 × 6, and 21 × 21 mm) were acquired from patients with diabetes using Topcon Triton before/after denoising. Perceived image quality was assessed by three ophthalmologists on a 5-point scale (capillary details in the superficial capillary plexus [SCP] and deep capillary plexus [DCP] of 3 × 3 and 6 × 6 mm scans, and vessel continuity and nonperfusion boundaries in 21 × 21 mm scans), and by objective metrics including contrast-to-noise ratio, peak signal-to-noise ratio, edge preservation index, and structural similarity index measurement. Diagnostic interpretability was evaluated through annotation of microaneurysm and vascular beading counts, foveal avascular zone margins, and peripheral nonperfusion borders. Quantitative reproducibility was assessed for vessel density, foveal avascular zone metrics (area, perimeter, circularity), and peripheral nonperfusion area delineations.

We included 145 eyes (mean patient age, 63.97 ± 9.25 years; 40.26% female) (35.17% no diabetic retinopathy, 33.10% nonproliferative diabetic retinopathy, and 31.72% proliferative diabetic retinopathy). Subjective vessel visualization improved in 3 × 3 (ΔSCP, 1.66 ± 0.39; ΔDCP, 1.90 ± 0.43), 6 × 6 (ΔSCP, 1.68 ± 0.36; ΔDCP, 2.11 ± 0.33), and 21 × 21 mm scans (Δvessels, 1.79 ± 0.37; Δnonperfusion, 1.61 ± 0.38) (all P < 0.001). Denoising objectively increased the contrast-to-noise ratio from poor (1.33-1.68) to moderate (2.90-3.97) (P < 0.001), and the peak signal-to-noise ratio (16.74-18.53 dB), structural similarity index measurement (0.60-0.72), and edge preservation index (0.71-0.79) reached moderate levels. Diagnostic interpretability showed most microaneurysms (64.17% SCP, 87.32% DCP) and venous beading (98.76%) remaining detectable. Vessel density decreased in 3 × 3 mm (ΔSCP, -5.81%; ΔDCP, -4.18%) and 6 × 6 mm scans (ΔSCP, -11.89%; ΔDCP, -5.23%; P < 0.001). The foveal avascular zone area increased slightly (Δ+0.01 mm²; P = 0.02), the perimeter expanded (Δ+0.53 mm; P < 0.001), and circularity decreased (Δ-0.16; P < 0.001), with similar peripheral nonperfusion area (Δ+4.84 mm²; P = 0.49).

N2V2 enhances OCTA quality and visualization, which may support more accurate retinal change assessments.

The N2V2 denoising algorithm can potentially advance the routine clinical use of OCTA by improving the visualization and features quantification.