Stepwise segmentation error correction in optical coherence tomography angiography images of patients with diabetic macular edema

Abstract

Aim: To determine the minimum number of optical coherence tomography B-scan corrections required to provide acceptable vessel density measurements on optical coherence tomography angiography images in eyes with diabetic macular edema.

Methods: In this prospective, noninterventional case series, the optical coherence tomography angiography images of eyes with center-involving diabetic macular edema were assessed. Optical coherence tomography angiography imaging was performed using RTVue Avanti spectral-domain optical coherence tomography system with the AngioVue software (V.2017.1.0.151; Optovue, Fremont, CA, USA). Segmentation error was recorded and manually corrected in the inner retinal layers in the central foveal, 100th and 200th optical coherence tomography B-scans. The segmentation error correction was then continued until all optical coherence tomography B-scans in whole en face image were corrected. At each step, the manual correction of each optical coherence tomography B-scan was propagated to whole image. The vessel density and retinal thickness were recorded at baseline and after each optical coherence tomography B-scan correction.

Results: A total of 36 eyes of 26 patients were included. To achieve full segmentation error correction in whole en face image, an average of 1.72 ± 1.81 and 5.57 ± 3.87 B-scans was corrected in inner plexiform layer and outer plexiform layer, respectively. The change in the vessel density measurements after complete segmentation error correction was statistically significant after inner plexiform layer correction. However, no statistically significant change in vessel density was found after manual correction of the outer plexiform layer. The vessel density measurements were statistically significantly different after single central foveal B-scan correction of inner plexiform layer compared with the baseline measurements (p = 0.03); however, it remained unchanged after further segmentation corrections of inner plexiform layer.

Conclusion: Multiple optical coherence tomography B-scans should be manually corrected to address segmentation error in whole images of en face optical coherence tomography angiography in eyes with diabetic macular edema. Correction of central foveal B-scan provides the most significant change in vessel density measurements in eyes with diabetic macular edema.

Keywords: artifact; diabetic macular edema; optical coherence tomography angiography; segmentation error; vessel density.

Figure 1.

En face optical coherence tomography angiography (OCTA), OCTA B-scan, and vessel density image of a patient with diabetic macular edema before [(a–c) for superficial capillary plexus and (g–i) for deep capillary plexus] and after [(d-f) for superficial capillary plexus and (j-l) for deep capillary plexus] segmentation error correction at the level of inner plexiform layer. The double arrow line shows the location of the corresponding OCT B-scan at the foveal center. Upper and lower dashed lines show 100th and 200th OCT B-scan locations.