Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation

Biwei Yin,Shams Kazmi,Austin B Mcelroy,Andrew K Dunn,Timothy Q Duong,Thomas E Milner,Roman V Kuranov

doi:10.1117/1.jbo.18.5.056005

Abstract

A swept-source dual-wavelength photothermal (DWP) optical coherence tomography (OCT) system is demonstrated for quantitative imaging of microvasculature oxygen saturation. DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitation. A 1,064-nm OCT probe and 770-nm and 800-nm photothermal excitation beams are combined in a single-mode optical fiber to measure microvasculature hemoglobin oxygen saturation (SO(2)) levels in phantom blood vessels with a range of blood flow speeds (0 to 17 mm/s). A 50-μm-diameter blood vessel phantom is imaged, and SO(2) levels are measured using DWP-OCT and compared with values provided by a commercial oximeter at various blood oxygen concentrations. The influences of blood flow speed and mechanisms of SNR phase degradation on the accuracy of SO(2) measurement are identified and investigated.

Highlights

We observed op signal amplitude in the phantom vessel containing blood resulting from photothermal excitation with 770-nm and 800-nm light
With the phantom vessel containing water, no op signal was detected in response to photothermal excitation
Three experiments were completed to investigate the functionality of the dual-wavelength photothermal (DWP)-optical coherence tomography (OCT) system: enface imaging of the blood vessel phantom, blood SO2 measurement without flow, and influence of blood flow speed on SO2 measurement

Summary

Introduction

Noninvasive quantitative evaluation of microvasculature hemoglobin oxygen saturation (SO2) in tissue is important in early detection and monitoring the progression of inflammatory and ischemic diseases such as cancer, stroke, and glaucoma.[1,2] Various approaches have been used to assess in vivo microvascular oxygen saturation, including oxygen-sensitive microelectrodes,[3,4,5,6,7] magnetic resonance imaging (MRI),[8,9,10,11,12] reflection spectroscopic oximetry.[13,14,15,16,17,18] and phosphorescence quenching.[17,19,20,21,22,23,24] Measurement by oxygen-sensitive microelectrodes is a point measurement method and is primarily limited to animal studies. MRI has limited spatial (100 to 150 μm) and temporal (tens of seconds to minutes) resolution. The phosphorescence quenching technique has limited spatial resolution (e.g., 50 μm), and no oxygen sensitive dyes that are approved by the United States Food and Drug Administration are available for clinical translation. A useful three-dimensional imaging technique, optical coherence tomography (OCT), was introduced in 1991 as a time domain approach[25] and was later used as a frequency domain method.[26,27] OCT implementation in the frequency domain improves signal-to-noise ratio and allows high-speed image acquisition. Huber et al showed that, for an equivalent signal-to-noise ratio, swept-source (SS) OCT with

Methods

Results

Conclusion