Spectroscopic OCT

Overview

Spectroscopic OCT (S-OCT) extends conventional OCT by extracting wavelength-dependent tissue optical properties from the broadband interference signal. This enables quantitative characterization of material composition, enabling distinguishing molecular species without the need for additional imaging modalities.

Technical Approach

The system uses on a swept-source OCT VCSEL laser operating at 1310 nm center wavelength with 100 nm bandwidth. Key innovations include:

Inverse algorithm design. We developed a Tikhonov-regularized spectral fitting framework that extracts depth-resolved scattering and absorption coefficients from the OCT signal. The algorithm handles the ill-posed nature of the inverse problem through joint regularization across wavelengths, exploiting the spectral smoothness of biological chromophores as a physical prior.

Polarization-sensitive extension. By incorporating Jones matrix analysis of the polarization state evolution through the catheter and tissue, we add birefringence as a third contrast mechanism alongside scattering and absorption. This is particularly valuable for characterizing collagen organization in fibrous caps.

Current Status

The inverse algorithm has been validated on tissue-mimicking phantoms with known optical properties, achieving relative reconstruction error below 5%.

Impact

Reliable, quantitative material characterization during imaging could transform a range of fields including biomedical imaging. Current clinical OCT provides structural images but cannot quantify tissue composition meaning that clinicians must infer plaque vulnerability from morphological features alone. S-OCT would provide direct biochemical contrast, enabling more accurate identification of vulnerable plaques and better-informed treatment decisions.