Purpose The objective of this research is to assess the feasibility of using fiber-based, diffuse optical spectroscopy (DOS) for quantitatively differentiating between stable and vulnerable atherosclerotic plaques.
Methods Diffuse optical spectroscopy (DOS) is a technique that combines experimental measurements and model-based data analysis to measure the bulk absorption (μa) and scattering (μs′) properties of highly scattering media. DOS typically uses red and near-infrared (NIR) light, especially from 600 to 1,000 nm, where light propagation in tissue is scattering dominated. Diffusive photons probe a large sample volume, providing macroscopically averaged absorption and scattering properties at depths up to a few centimeters. In this study we used a probe developed at Beckman Laser Institute to measure optical properties of a 3 cm × 4 cm sample from ex vivo human aorta obtained from UCIMC that was diagnosed with atherosclerosis postmortem.
Results There were three histologically different tissue types in the sample. The tissue types were type V with a thin cap, type V with a thick cap, and type VI atherosclerotic lesions. The quantitative spectroscopic results indicate that in terms of scattering properties of the sample tissue, type V (large cap) scatters more than type V (thin cap), which, in turn, scatters more than type VI. This property reveals information about tissue structure. On the other hand, the absorption spectra of the sample, which reveals information about the biochemical composition, has the opposite pattern; type VI absorbs more than type V (thin cap), which absorbs more than type V (large cap).
Conclusion The three tissue types all showed different scattering and absorption spectra at different near-infrared wavelengths. Therefore, it may be possible to differentiate between stable and vulnerable atherosclerotic plaques using the fiber-based DOS probe in steady-state frequency domain photon migration (SS-FDPM).
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