Enhancing visibility of choroidal vasculature in OCT via attenuation compensation and coherence transport inpainting

Abstract

Purpose : Choroidal vasculature plays important roles in revealing the mechanisms of various ocular diseases. OCT imaging is capable of resolving the three-dimensional information of choroid. However, some instinct defects of this imaging technique, such as sensitivity roll-off and the vessel shadows from outer retina, degrade the visibility of choroidal vasculature. Image processing methods combining attenuation compensation (AC) and coherence transport inpainting (CTI) is proposed to remove the projection artifacts without the loss of underlying structure and enhance small choroidal vessels.

Methods : 3×3 mm² FOV volumetric scans centered on the macula of healthy volunteers were taken with a Topcon 100-kHz swept source OCT system. We applied the AC method on RPE-flattened data sets, which further improves the graph-search-based segmentation of choroid-sclera boundary. Mean projection along the axial direction was calculated to derive the distribution of the retinal vessel shadows (between RPE and Bruch’s membrane) and the en face choroid (between Bruch’s membrane and the choroid-sclera boundary). We segmented the vessel shadow by using a using a weighted symmetry filter to generate a shadow mask. The mask combining with the mean-projected choroid were employed to calculate the shadow-free choroidal vasculature via the CTI algorithm.

Results : Applying the AC could enhance weak vessel signals and also remove part of the shadows generated by small vessels, while the shadows of the large vessels still overlay on the choroidal vasculature. The CTI could further eliminate the residual shadows and keep the morphology of the underneath choroidal vessels.

Conclusions : Combing the AC and CTI could effectively enhance the visibility of the choroidal vasculature, which could benefit the pathology studies related to choroid.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Flowchart demonstration of the proposed methods.

 

Enhanced choroidal vasculature using the proposed methods.