Impact of Multiple En Face Image Averaging on Quantitative Assessment from Optical Coherence Tomography Angiography Images

Akihito Uji; Siva Balasubramanian; Jianqin Lei; Elmira Baghdasaryan; Mayss Al-Sheikh; SriniVas R Sadda

doi:10.1016/j.ophtha.2017.02.006

Impact of Multiple En Face Image Averaging on Quantitative Assessment from Optical Coherence Tomography Angiography Images

Ophthalmology. 2017 Jul;124(7):944-952. doi: 10.1016/j.ophtha.2017.02.006. Epub 2017 Mar 17.

Authors

Akihito Uji¹, Siva Balasubramanian¹, Jianqin Lei¹, Elmira Baghdasaryan¹, Mayss Al-Sheikh¹, SriniVas R Sadda²

Affiliations

¹ Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California; Department of Ophthalmology, David Geffen School of Medicine at the University of California-Los Angeles, Los Angeles, California.
² Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California; Department of Ophthalmology, David Geffen School of Medicine at the University of California-Los Angeles, Los Angeles, California. Electronic address: ssadda@doheny.org.

PMID: 28318637
DOI: 10.1016/j.ophtha.2017.02.006

Abstract

Purpose: To investigate the impact of multiple en face image averaging on quantitative measurements of the retinal microvasculature using optical coherence tomography angiography (OCTA).

Design: Prospective, observational, cross-sectional case series.

Participants: Twenty-one healthy individuals with normal eyes.

Methods: Macular OCTA images were acquired from all participants using the Zeiss Cirrus 5000 with Angioplex OCTA software (Carl Zeiss Meditec, Dublin, CA). Nine OCTA cube scans per eye were obtained and 9 superficial retinal layer (SRL) and deep retinal layer (DRL) en face OCTA image slabs were averaged individually after registration. Quantitative parameters from the retinal microvasculature were measured on binarized and skeletonized OCTA images and compared with single OCTA images without averaging.

Main outcome measures: Vessel density (VD), vessel length density (VLD), vessel diameter index (VDI), and fractal dimension (FD).

Results: Participants with artifact or poor image quality were excluded, leaving 18 eyes for the analysis. After averaging, qualitatively there was apparent reduction in background noise, and fragmented vessels in the images before averaging became continuous with smoother walls and showed sharper contrast in both the SRL and DRL. Binarized and skeletonized derivates of these averaged images also showed fewer line fragments and dots in nonvascular areas and more continuous vessel images than those of images without averaging. In both SRL and DRL, VD (P = 0.0010 and P = 0.0003, respectively), VLD (P < 0.0001 for both), and FD (P < 0.0001 for both) significantly decreased and VDI significantly increased after averaging (P < 0.0001 for both).

Conclusions: Averaging of multiple en face OCTA images improves image quality and also significantly impacts quantitative measurements. Reducing noise that could be misinterpreted as flow and annealing discontinuous vessel segments seem to be major mechanisms by which averaging may be of benefit.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Artifacts
Cross-Sectional Studies
Female
Fluorescein Angiography / methods*
Fundus Oculi
Healthy Volunteers
Humans
Male
Microvessels / diagnostic imaging
Middle Aged
Prospective Studies
Reproducibility of Results
Retinal Vessels / diagnostic imaging*
Tomography, Optical Coherence / methods*
Young Adult