Fishing for confidence A theoretical and experimental framework for precise water content determination using optical coherence tomography

Optical Coherence Tomography (OCT) is a non-invasive imaging technique widely employed in medical diagnostics to generate high-resolution cross-sectional images and provide detailed insights into tissue properties. This thesis focuses on the precise measurement of the attenuation coefficient (μ_OCT), an optical property that quantifies the reduction in light intensity due to absorption and scattering, and explores its application in evaluating tissue hydration, a critical factor in medical diagnostics and patient care.
This research establishes the requirements for hydration assessment using μ_OCT, demonstrating that at least three wavelengths are necessary to precisely account for wavelength-dependent scattering and absorption effects. To achieve a clinically relevant hydration measurement precision of 2%, μ_OCT must be measured with a precision better than 0.01 mm⁻¹.
To achieve this level of precision, the study develops a theoretical framework grounded in a maximum likelihood approach, resulting in the derivation of an analytical equation for high-precision μ_OCT measurement and was confirmed through simulations.
Experimental validation was performed with a custom-built OCT system operating at 1310 nm, achieving an unprecedented standard deviation below 0.01 mm⁻¹ for diluted intralipid samples. Furthermore, a custom triple-wavelength OCT setup, using 1064 nm, 1310 nm, and 1550 nm, is proposed to enable precise water fraction determination by addressing wavelength-specific scattering and absorption effects.
In summary, this thesis provides a robust theoretical and experimental framework for high-precision attenuation coefficient measurements using OCT. It sets a new standard for high precision μ_OCT determination and demonstrates the potential of OCT for clinically relevant hydration assessment.