Spectroscopic OCT

What is Spectroscopic OCT?

Spectroscopic OCT (S-OCT) extends conventional OCT by extracting wavelength-dependent tissue optical properties from the acquired broadband interference signal allowing for quantitative composition, not just structure, from the same measurement.

The inverse problem

The imaging system used a swept-source OCT VCSEL laser operating at 1310 nm with a 100 nm bandwidth. The important details:

Inverse algorithm design. I developed a spectral fitting approach that allows for the determination of depth-resolved scattering and absorption coefficients from an OCT interferogram.

Where it stands

The inverse algorithm has been validated on tissue-mimicking phantoms with known optical properties. The challenge of signal-to-noise ratio (SNR) and the possible effects of polarization-based artifacts introduced by optical elements still exist.

Why this matters

Clinical OCT shows a cardiologist the shape of a plaque but not what it is made of, so vulnerability gets inferred from morphology alone unless OCT is used in combination with near infrared spectroscopy (NIRS) which can be expensive. Depth-resolved absorption and scattering would let the same catheter pull-back tell you something about composition, lipid versus fibrous cap, without adding hardware. Whether the contrast survives in vivo conditions (motion, blood clearing, polarization effects in the catheter) is the open question.