Common-path phase-sensitive optical coherence tomography provides enhanced phase stability and detection sensitivity for dynamic elastography.

Gongpu Lan,Michael D Twa,Manmohan Singh,Kirill V Larin

doi:10.1364/boe.8.005253

Abstract

Phase-sensitive optical coherence elastography (PhS-OCE) is an emerging optical technique to quantify soft-tissue biomechanical properties. We implemented a common-path OCT design to enhance displacement sensitivity and optical phase stability for dynamic elastography imaging. The background phase stability was greater in common-path PhS-OCE (0.24 ± 0.07nm) than conventional PhS-OCE (1.60 ± 0.11μm). The coefficient of variation for surface displacement measurements using conventional PhS-OCE averaged 11% versus 2% for common-path PhS-OCE. Young's modulus estimates showed good precision (95% CIs) for tissue phantoms: 24.96 ± 2.18kPa (1% agar), 49.69 ± 4.87kPa (1.5% agar), and 116.08 ± 12.14kPa (2% agar), respectively. Common-path PhS-OCE effectively reduced the amplitude of background dynamic optical phase instability to a sub-nanometer level, which provided a larger dynamic detection range and higher detection sensitivity for surface displacement measurements than conventional PhS-OCE.

Highlights

A hallmark of disease is a change in the physical properties of affected tissues, e.g. change in stiffness due to tumor, swelling, or inflammation [1, 2]
If the tissue deformation induced during elastography imaging is on the order of microns or less, it may fall below the detection capabilities of structural optical coherence tomography (OCT) imaging
Swept-source light sources with multi-MHz A-scan rates have been developed [22, 46], which enables nearly real-time optical elastography, which will enable detection of elastic wave propagation with single-shot excitation. This common-path strategy can be implemented for swept-source OCT/Optical coherence elastography (OCE) imaging modalities to reduce the effect of the local vibration existing between the sample and reference arms, and to enhance the system’s phase stability

Summary

Introduction

A hallmark of disease is a change in the physical properties of affected tissues, e.g. change in stiffness due to tumor, swelling, or inflammation [1, 2]. Optical coherence elastography (OCE) is one of several elasticity imaging techniques designed to provide quantitative measurements of tissue biomechanical properties [5] Because it is based on optical interferometry, OCE offers greater axial and lateral spatial resolution, compared to ultrasound elastography [6,7,8], or magnetic resonance elastography [9, 10]. The promise of this non-invasive imaging-based technology is that it can provide quantitative, in vivo diagnostic information that may be useful for earlier disease detection and more precise guidance on the response to treatment [4]. By analyzing the complex component of the OCT signal, phasesensitive OCT (PhS-OCT) [12,13,14,15,16] can provide much greater sample displacement sensitivity (nanometer-scale) [3, 12, 17,18,19,20,21,22] and direct quantitative measurements of the displacement along the optical axis, which enables the visualization and analysis of the shear wave propagation in dynamic OCE [4, 23]

Methods

Results

Conclusion