Efficacy and Reproducibility of Attenuation-Compensated Optical Coherence Tomography for Assessing External Elastic Membrane Border and Plaque Composition in Native and Stented Segments　- An In Vivo and Histology-Based Study.

Background: Attenuation-compensated (AC) technique was recently introduced to improve the plaque characterization of optical coherence tomography (OCT). Histological validation demonstrated promising results but the efficacy and reproducibility of this technique for assessing in-vivo tissue composition remains unclear. Methods and Results: OCT images portraying native (n=200) and stented (n=200) segments and 31 histological cross-sections were analyzed. AC-OCT appeared superior to conventional (C)-OCT in detecting the external elastic lamina (EEM) borders (76% vs. 65.5%); AC-OCT enabled larger EEM arc detection compared with C-OCT (174.2 +/- 58.7 degrees vs. 137.5 +/- 57.9 degrees; P<0.001). There was poor agreement between the 2 techniques for detection of lipid in native and lipid and calcific tissue in stented segments (kappa range: 0.164-0.466) but the agreement of C-OCT and AC-OCT was high for calcific tissue in native segments (kappa=0.825). Intra and interobserver agreement of the 2 analysts was moderate to excellent with C-OCT (. range: 0.681-0.979) and AC-OCT (kappa range: 0.733-0.892) for all tissue types in both native and stented segments. Ex-vivo analysis demonstrated that C-OCT was superior to AC-OCT (kappa=0.545 vs. kappa=0.296) for the detection of the lipid component in native segments. Conclusions: The AC technique allows better delineation of the EEM but it remains inferior for lipid pool detection and neointima characterization. Combined AC- and C-OCT imaging may provide additional value for complete assessment of plaque and neointima characteristics.