2D Modeling and Correction of Fan-Beam Scan Geometry in OCT

Abstract

A-scan acquisitions in OCT images are acquired in a fan-beam pattern, but saved and displayed in a rectangular space. This results in an inaccurate representation of the scan geometry of OCT images, which introduces systematic distortions that can greatly impact shape and morphology based analysis of the retina. Correction of OCT scan geometry has proven to be a challenging task due to a lack of information regarding the true angle of entry of each A-scan through the pupil and the location of the A-scan nodal points. In this work, we present a preliminary model that solves for the OCT scan geometry in a restricted 2D setting. Our approach uses two repeat scans with corresponding landmarks to estimate the necessary parameters to correctly restore the fan-beam geometry of the input B-scans. Our results show accurate estimation of the ground truth geometry from simulated B-scans, and we found qualitatively promising result when the correction was applied to longitudinal B-scans of the same subject. We establish a robust 2D framework that can potentially be expanded for full 3D estimation and correction of OCT scan geometries.