Improved arterial tissue differentiation by spectroscopic optical coherence tomography

Abstract

Optical coherence tomography (OCT) is a relatively new imaging modality similar with ultrasound where the sound waves are replaced by ballistic photons. OCT provides images at high spatial resolution which allow for the identification of micron size morphological tissue structures. A high impact application is visualization of arterial wall and atherosclerotic plaques. Despite high spatial resolution to complete the transfer of this imaging modality into clinical environment there is a need for markers which would quantify the physiological condition of the sample. Finding the proper markers is a topic of high interest for many research groups. A potential marker suggested by the OCT community is the optical attenuation coefficient. Although OCT image itself provides important diagnostic and structural information there are also new methods of tissue characterization that have been developed through spectroscopic OCT and quantitative OCT. Spectroscopic OCT investigates the spectral response while the quantitative OCT extends the investigation to non-spectral parameters. Here we investigate two procedures for calculation of optical attenuation coefficient dependence versus wavelength. The wavelength analysis will provide new insight into the chemical nature of the sample, because the spectral backreflected signal depends on sample absorption and scattering properties. In this study we demonstrate the application of OCT for quantitative and spectral analysis of vulnerable plaque morphology on Watanabe heritable hyperlipidemic - myocardial infarction (WHHLMI) rabbit model. The results suggest that the spectral dependence of the derived OCT attenuation coefficient can be used for tissue differentiation. We demonstrated that differences and the spectral dependence of the optical attenuation coefficient are linked to the macrophage content of the region of interest.