Approaches to quantify optical coherence tomography angiography metrics

Bingyao Tan; Ralene Sim; Jacqueline Chua; Damon W K Wong; Xinwen Yao; Gerhard Garhöfer; Doreen Schmidl; René M Werkmeister; Leopold Schmetterer

doi:10.21037/atm-20-3246

Approaches to quantify optical coherence tomography angiography metrics

Ann Transl Med. 2020 Sep;8(18):1205. doi: 10.21037/atm-20-3246.

Authors

Bingyao Tan^{1

2

3}, Ralene Sim², Jacqueline Chua^{2

4}, Damon W K Wong^{1

2

3}, Xinwen Yao^{1

2

3}, Gerhard Garhöfer⁵, Doreen Schmidl⁵, René M Werkmeister⁶, Leopold Schmetterer^{2

3

4

5

6

7

8

9}

Affiliations

¹ Institute for Health Technologies, Nanyang Technological University, Singapore, Singapore.
² Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
³ SERI-NTU Advanced Ocular Engineering (STANCE) Program, Nanyang Technological University, Singapore, Singapore.
⁴ Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
⁵ Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
⁶ Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
⁷ Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.
⁸ Department of Ophthalmology, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.
⁹ Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland.

Abstract

Optical coherence tomography (OCT) has revolutionized the field of ophthalmology in the last three decades. As an OCT extension, OCT angiography (OCTA) utilizes a fast OCT system to detect motion contrast in ocular tissue and provides a three-dimensional representation of the ocular vasculature in a non-invasive, dye-free manner. The first OCT machine equipped with OCTA function was approved by U.S. Food and Drug Administration in 2016 and now it is widely applied in clinics. To date, numerous methods have been developed to aid OCTA interpretation and quantification. In this review, we focused on the workflow of OCTA-based interpretation, beginning from the generation of the OCTA images using signal decorrelation, which we divided into intensity-based, phase-based and phasor-based methods. We further discussed methods used to address image artifacts that are commonly observed in clinical settings, to the algorithms for image enhancement, binarization, and OCTA metrics extraction. We believe a better grasp of these technical aspects of OCTA will enhance the understanding of the technology and its potential application in disease diagnosis and management. Moreover, future studies will also explore the use of ocular OCTA as a window to link ocular vasculature to the function of other organs such as the kidney and brain.

Keywords: Optical coherence tomography angiography (OCTA); image processing; ocular imaging.

Publication types

Review