Background: The aim of this study was to investigate the accuracy of optical frequency domain imaging (OFDI) in lipid-rich plaque detection and determine the causes of "misinterpretation," and evaluate whether these limitations can be overcome with intravascular ultrasound (IVUS) using ex-vivo human coronaries.
Methods and results: The OFDI images and corresponding 218 histological segments were evaluated. Segments with a poor signal and diffuse borders on OFDI, classified as lipid-rich plaques, were compared with the histological segments and IVUS images. Using histological images as the gold standard, the sensitivity, specificity, positive predictive value, and negative predictive value of OFDI for the detection of lipid-rich plaques were 93%, 93%, 85%, and 97%, respectively. The causes of false-positive diagnosis of lipid-rich plaque (11 segments) were superficial macrophage infiltration causing signal attenuation (8/11 segments, 73%) and tangential signal dropout of light (3/11 segments, 27%), whereas the cause of false-negative diagnosis was thickening of the fibrous cap (5 segments, 100%). Simultaneous IVUS helped to correct the misinterpretation of OFDI results and improved the diagnostic accuracy; the sensitivity, specificity, positive predictive value, and negative predictive value of OFDI with adjunct use of IVUS were 96%, 99%, 99%, and 98%, respectively.
Conclusions: OFDI occasionally over- or underestimates the existence of lipid-rich plaques, which may be overcome with adjunctive usage of IVUS.