Functional imaging of dye concentration in tissue phantoms by spectroscopic optical coherence tomography

Abstract

We present functional imaging of the concentration of a photodynamic therapy (PDT)-related dye in scattering tissue phantoms based on spatially resolved measurements of optical properties through spectroscopic optical coherence tomography (OCT). Expressions for the OCT signal are developed, enabling estimation of depth-resolved sample optical properties. Based on these expressions, we discuss speckle statistics and speckle correlations of the OCT signal. Speckle noise reduction is performed by spatial filtering and is used to improve accuracy in the estimated optical properties at the expense of spatial resolution. An analytic expression for the precision in the estimated optical properties is derived. This expression shows that axial filtering, and thereby a reduction of axial resolution, gives a larger improvement in precision compared to the same filtering and reduction in the transversal resolution. It also shows that imaging with a shorter coherence length, or a larger numerical aperture, improves precision when the filter length determines the spatial resolution. Good agreement is obtained between experimentally determined and theoretically predicted variance in the estimated attenuation coefficients and dye concentration. Finally, we present guidelines for spectroscopic OCT systems for concentration imaging and discuss application of the method to more realistic phantoms and tissue.

Optical coherence tomography: a review of clinical development from bench to bedside

“…187 This principle could potentially be used to track photodynamic therapy dyes during treatment, a concept that was recently demonstrated in tissue phantoms. 188…”

Magnetic protein microspheres as dynamic contrast agents for magnetomotive optical coherence tomography

“…A second novel method is a functional OCT modality called magnetomotive OCT (MM-OCT) which makes use of an external magnetic field to magnetically modulate its corresponding contrast agent to induce the displacement of nearby scatterers (32,33). Spectroscopic OCT (S-OCT), which is being researched by multiple groups, has shown some promising success in being able to provide quantitative information about the biochemical makeup or the presence of NIR dyes in the specimen as well as in the concentration of hemoglobin (28,35,36). Polarization-sensitive OCT (PS-OCT) is another functional mode of OCT which measures the birefringence of the tissue (24).…”

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“…The available spectroscopy has helped many successful applications such as tissue functionality characterization [3], cell molecules differentiation [4], cancerous diseases diagnosis [5], and detection of anomalies in tissues [6]. These successes are attributed to the advantage of using spectroscopy to classify different scatterers.…”