Motion Estimation for Optical Coherence Elastography Using Signal Phase and Intensity

TL;DR

This paper introduces a robust OCT displacement estimation method combining phase and intensity data, effectively tracking large displacements with high precision, surpassing conventional techniques especially for movements exceeding half the wavelength.

Contribution

A novel optimization-based approach that jointly uses phase and intensity information for improved displacement tracking in OCT imaging, handling larger displacements and phase wrapping issues.

Findings

Outperforms conventional methods in axial tracking precision

Effective for displacements larger than half the wavelength

Utilizes dynamic programming for joint phase and intensity analysis

Abstract

Displacement estimation in optical coherence tomography (OCT) imaging is relevant for several potential applications, e.g. for optical coherence elastography (OCE) for corneal biomechanical characterization. Larger displacements may be resolved using correlation-based block matching techniques, which however are prone to signal de-correlation and imprecise at commonly desired sub-pixel resolutions. Phase-based tracking methods can estimate tiny sub-wavelength motion, but are not suitable for motion magnitudes larger than half the wavelength due to phase wrapping and the difficulty of any unwrapping due to noise. In this paper a robust OCT displacement estimation method is introduced by formulating tracking as an optimization problem that jointly penalizes intensity disparity, phase difference, and motion discontinuity. This is then solved using yynamic programming, utilizing both sub-wavelength-scale phase and pixel-scale intensity information from OCT imaging, while inherently seeking for the number of phase wraps. This allows for effectively tracking axial and lateral displacements, respectively, with sub-wavelength and pixel scale resolution. Results with tissue mimicking phantoms show that our proposed approach substantially outperforms conventional methods in terms of axial tracking precision, in particular for displacements exceeding half the imaging wavelength.