Combined optical coherence tomography and intravascular ultrasound radio frequency data analysis for plaque characterization. Classification accuracy of human coronary plaques in vitro

Abstract

This study was performed to characterize coronary plaque types by optical coherence tomography (OCT) and intravascular ultrasound (IVUS) radiofrequency (RF) data analysis, and to investigate the possibility of error reduction by combining these techniques. Intracoronary imaging methods have greatly enhanced the diagnostic capabilities for the detection of high-risk atherosclerotic plaques. IVUS RF data analysis and OCT are two techniques focusing on plaque morphology and composition. Regions of interest were selected and imaged with OCT and IVUS in 50 sections, from 14 human coronary arteries, sectioned post-mortem from 14 hearts of patients dying of non-cardiovascular causes. Plaques were classified based on IVUS RF data analysis (VH-IVUS(TM)), OCT and the combination of those. Histology was the benchmark. Imaging with both modalities and coregistered histology was successful in 36 sections. OCT correctly classified 24; VH-IVUS 25, and VH-IVUS/OCT combined, 27 out of 36 cross-sections. Systematic misclassifications in OCT were intimal thickening classified as fibroatheroma in 8 cross-sections. Misclassifications in VH-IVUS were mainly fibroatheroma as intimal thickening in 5 cross-sections. Typical image artifacts were found to affect the interpretation of OCT data, misclassifying intimal thickening as fibroatheroma or thin-cap fibroatheroma. Adding VH-IVUS to OCT reduced the error rate in this study.

Fig. 1

Chart of misclassifications; the arrows indicate the misclassification of histology-characterized lesions by the respective imaging techniques. The thickness of the arrow represents the frequency in the data set, which is also indicated by the numbers on the arrows. For example: of the lesions that were identified as IT in histology, 8 were interpreted as FA in OCT. Only misclassifications occurring more than twice are included in the figure. IT intimal thickening, FA fibroatheroma

Fig. 2

a Histology of a calcified fibroatheroma. b Corresponding VH-IVUS classified as calcified fibroatheroma. c Corresponding OCT classified as calcified fibroatheroma. The needle used to mark the site can be seen in the bright feature at 6 o’clock in OCT, as well as in the appearance of dense calcium in that location in VH-IVUS