Measurement of the thickness of the fibrous cap by optical coherence tomography

Identification of the fibrous cap is important because its thickness is a major determinant of plaque vulnerability in lipid-rich plaque. Thus, a high-resolution imaging technique may be a promising method for the identification of the fibrous cap within lipid-rich plaque. The purpose of this study was to investigate the feasibility of using optical coherence tomography (OCT) to measure the thickness of the fibrous cap within lipid-rich plaque. We examined 35 lipid-rich plaques from 102 coronary arterial segments of 38 human cadavers (22 men and 16 women; mean ages, 74 ± 7 years). Optical coherence tomography and corresponding histological images were digitized for measurement of the thickness of fibrous cap, and the results between OCT and histological examination were compared. There was good correlation of the thickness of the fibrous cap between OCT and histological examination ( y = 0.97 x + 28.49; r = 0.90; P < .001). A Bland-Altman test showed good agreement of the thickness of the fibrous cap between OCT and histological examination (mean difference, −24 ± 44 μm). Optical coherence tomography provides an accurate representation of the thickness of the fibrous cap and may prove useful in assessing plaque vulnerability in lipid-rich plaque.