Key result
Cross-polarization OCT differentiates stable from unstable plaques using integral depolarization factor and effective birefringence.
p-value: p=<0.05
Quantitative evaluation of CP OCT images using idF and Δn can differentiate between stable and unstable ex vivo coronary atherosclerotic plaques.
Ex vivo CP OCT metrics may characterize plaque stages; leaves open in vivo validation for unstable plaque detection.
The aim of the investigation was to develop an approach to quantitative evaluation of polarization properties (birefringence and crossscattering) basing on cross-polarization oCT images (CP oCT) in order to characterize the development stages of atherosclerotic plaques and to reveal unstable ones. Materials and Methods.We report on quantitative analysis of CP oCT images of the seven development stages of atherosclerotic plaques ex vivo.integral depolarization factor (idF) and effective birefringence coefficient (Δn) were proposed as parameters for quantitative characterization of the CP oCT images.Results.Calculation of the idF and Δn in the local region of interest (intima/fibrous cap) showed a statistically relevant difference between stable (stage iV) and unstable (stage Va) plaques (0.46±0.21 against 0.09±0.04for idF and (0.47±0.10)•10 -3 against (0.25±0.07)•10 -3 for Δn; p<0.05). it was found that Δn value in the range (0.22-0.29)•10 -3 (within the limits of two standard deviations) indicates the presence of only a small amount of highly organized collagen in the fibrous cap of an unstable plaque which can indicate its tendency to rupture.We believe that these changes are connected with the prevalence of disorganized fibers during the inflammatory process in the fibrous cap of an unstable plaque, and to the presence of clusters of foam cells and inflammatory cells between them. Conclusion.The proposed approach to the quantitative evaluation of CP oCT images (calculation of idF and building Δn maps) allows to assess both cross-scattering and birefringence of atherosclerotic plaques at various development stages and more reliably reveal their vulnerability.
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Gubarkova et al. (2015) studied Atherosclerotic plaques. Cross-polarization OCT (CP OCT) imaging vs. Stable plaques was evaluated on Integral depolarization factor (idF) and effective birefringence coefficient (Δn) (p=<0.05). Cross-polarization OCT imaging revealed significant differences in integral depolarization factor (0.46 vs 0.09) and effective birefringence coefficient between stable and unstable plaques (p<0.05).
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