Analysis of image formation in optical coherence elastography using a multiphysics approach.

Lixin Chin,David D Sampson,Peter R T Munro,Barry J Doyle,Brendan F Kennedy,Robert A Mclaughlin,Andrea Curatolo

doi:10.1364/boe.5.002913

Abstract

IMAGE FORMATION IN OPTICAL COHERENCE ELASTOGRAPHY (OCE) RESULTS FROM A COMBINATION OF TWO PROCESSES: the mechanical deformation imparted to the sample and the detection of the resulting displacement using optical coherence tomography (OCT). We present a multiphysics model of these processes, validated by simulating strain elastograms acquired using phase-sensitive compression OCE, and demonstrating close correspondence with experimental results. Using the model, we present evidence that the approximation commonly used to infer sample displacement in phase-sensitive OCE is invalidated for smaller deformations than has been previously considered, significantly affecting the measurement precision, as quantified by the displacement sensitivity and the elastogram signal-to-noise ratio. We show how the precision of OCE is affected not only by OCT shot-noise, as is usually considered, but additionally by phase decorrelation due to the sample deformation. This multiphysics model provides a general framework that could be used to compare and contrast different OCE techniques.

Highlights

Optical coherence elastography (OCE) is a technique in which an image is formed of a mechanical property of a sample
Several groups have previously analyzed aspects of the elastogram formation process, including recent studies focused on the detection of sample displacement [3, 19, 20] and earlier studies examining the mechanical deformation of samples [21,22,23]
We show that the displacement sensitivity, and the precision, is affected by optical noise, as is generally considered [3, 10, 12, 13, 23, 27], but by “phase decorrelation noise”, which results from a violation of the assumption, when measuring displacement from optical coherence tomography (OCT) scans, that sample deformation preserves phase correlation

Summary

Introduction

Optical coherence elastography (OCE) is a technique in which an image (elastogram) is formed of a mechanical property of a sample. In OCE, a mechanical load is applied to a sample, and the resulting deformation is detected using optical coherence tomography (OCT) [1]. Several groups have previously analyzed aspects of the elastogram formation process, including recent studies focused on the detection of sample displacement [3, 19, 20] and earlier studies examining the mechanical deformation of samples [21,22,23]. These studies have largely considered the processes of deformation and detection as independent

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