Precision of attenuation coefficient measurements by optical coherence tomography

Area of Science:

• Biomedical Optics
• Medical Imaging
• Optical Engineering

Background:

• Optical Coherence Tomography (OCT) is a key imaging technique for microscopic tissue analysis.
• OCT signal analysis quantifies optical properties like attenuation coefficients, crucial for understanding tissue structure.
• A standardized measure for the precision of OCT-derived optical properties is currently lacking.

Purpose of the Study:

• To present a robust theoretical framework for calculating the precision of OCT-derived optical attenuation coefficients.
• To establish the Cramér-Rao lower bound (σμOCT) as a measure for OCT precision.
• To address the need for standardized precision metrics in OCT-based tissue characterization.

Main Methods:

• Derived an analytical solution for σμOCT using maximum likelihood estimation and Fisher information, assuming known focus position and depth.
• Validated the analytical solution using simulated OCT signals with a least-squares fitting procedure.
• Investigated the impact of shot noise and focus position uncertainty on precision.

Main Results:

• The analytical solution for σμOCT perfectly matched simulated data without shot noise.
• The solution remains accurate for signal-to-noise ratios (SNRs) above 20 dB in the presence of shot noise.
• Numerical calculations confirmed agreement with σμOCT for lower SNRs and unknown focus positions.

Conclusions:

• The analytical solution offers a fast, rigorous, and user-friendly method for measuring OCT-derived attenuation coefficients at SNRs > 20 dB.
• Investigated the influence of focal point uncertainties on attenuation coefficient precision.
• The framework is extendable to assess uncertainties in other OCT system parameters.