Choroidal neovascularization imaging using multiple en face optical coherence tomography angiography image averaging

To determine the effects of averaging five en face optical coherence tomography angiographic (OCTA) images on the quality of the images in eyes with a choroidal neovascularization (CNV).Twenty-seven eyes of 25 patients (18 men, 7 women; average age 71.0 years) with a CNV were examined by OCTA (OCT HS-100, Canon. Japan). A 3 × 3-mm image including the CNV was recorded and automatically segmented between the retinal outer layers. Analyses were performed on a single image (S-image) and the average of five single images of the same area (A-images). The region of the CNV was selected by ImageJ, and the peak signal-to-noise ratio (PSNR), the vascular density (VD), fractal dimension (FD), and the noise component using band pass filter (BPF) processing of the S- and A-images of each case were compared.The average PSNR for the A-images was 14.0 which was significantly higher than the 12.2 for the S-images (P 0.01). However, the average VD was 33.6% for the S-images and 34.8% for the A-images (P 0.1). The average FD was 1.67 for the S-images and 1.54 for the A-images (P 0.01). The mean luminance difference obtained by subtracting the luminance of the A-image from the S-image after BPF processing was 10.41 ± 14.66 db which was positive for all eyes.The better quality of the A-images of a CNV and absence of a significant difference in the vascular density indicates that the improvement was due to the removal of the same signal levels of the noise component and blood vessels.