Abstract
Non-invasive depth-resolved measurement of hemoglobin oxygen saturation (SaO2) levels in discrete blood vessels may have implications for diagnosis and treatment of various pathologies. We introduce a novel Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) for non-invasive depth-resolved measurement of SaO2 levels in a blood vessel phantom. DWP OCT SaO2 is linearly correlated with blood-gas SaO2 measurements. We demonstrate 6.3% precision in SaO2 levels measured a phantom blood vessel using DWP-OCT with 800 and 765 nm excitation wavelengths. Sources of uncertainty in SaO2 levels measured with DWP-OCT are identified and characterized.
Highlights
Tissue oxygenation is an important physiological parameter
We introduce a Dual-Wavelength Photothermal Optical Coherence Tomography (OCT) (DWP-OCT) that uses excitation and probe light in the near infrared spectral region for depth-resolved SaO2 monitoring in tissue phantoms
The experimental setup for our DWP-OCT (Fig. 1) system to measure SaO2 levels contains three major components: 1) excitation laser (800 nm or 765 nm) and fiber delivery system to induce nanometer-scale optical pathlength changes in the blood sample; 2) sample consisting of a non-absorbing polytetrafluoroethylene (PTFE) conduit containing blood with variable
Summary
Tissue oxygenation is an important physiological parameter. Abnormal oxygenation of tissues and blood has been implicated in a number of diseases preceding irreversible tissue damage including cancer, inflammatory and infectious processes, diabetic retinopathy, choroidal disorders, stroke and vascular dementia among others [1]. Distinct differences in the absorption spectra between oxy- and deoxy-hemoglobin in the visible and infrared (IR) spectral regions underlie spectroscopic methods for non-invasive assessment of in vivo hemoglobin oxygen saturation levels [2,3,4,5,6,7,8,9,10,11] Because these spectroscopic methods provide mean arterial and venous [2,3,4,5,6,7,8] and arterial [9,10,11] SaO2 levels averaged over a relatively large volume of tissue, longitudinal and lateral spatial specificity to identify a damaged tissue volume is compromised. Our approach was applied to depth-resolved measurement of graded SaO2 levels in phantoms and does not suffer from the high signal variability of spectral OCT approaches
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