Abstract 15890: Not all Intravascular Optical Coherence Tomography Bright Spots are Macrophages: A Quantitative Study
Background: Methods to quantify the presence of macrophages in intravascular optical coherence tomography (IVOCT) images are lacking. We developed a quantitative algorithm to identify bright spots in IVOCT images that accounts for depth in tissue, distance from light source, and signal-to-noise ratio and compared the results of this technique to histologic examination. Using this algorithm, we tested the hypothesis that since bright spots are caused by differences in indices of refraction (IR), that other plaque components besides foam cells situated near a fibrous caps would generate bright spots.
Methods: Fresh human cadaver coronary arteries (n=6) were imaged with IVOCT in a mock catheterization laboratory. We performed a quantitative bright spot analysis and compared it to the histologic composition of matching tissue sections.
Results: Our algorithm identified 212 regions of distinct bright spots. We showed that macrophage-rich areas co-localized with bright spots in 21% of cases. However, additional etiologies were identified to cause bright spots including: fibrous tissue mixed with proteoglycans (22%), mesh-like fibrous tissue (14%), areas of tissue interface or plaque layering (36%), and lipid in calcified cores (7%). Additionally, we found large pools of macrophages that caused shadows—not bright spots. Results are summarized in the Table.
Conclusions: Using our novel quantitative technique, we showed that bright spots in IVOCT images are caused by combinations of plaque components that create sharp changes in the IR. Software that incorporates these methods may improve the identification of some types of vulnerable plaque and allow standardization of image interpretation by clinicians using IVOCT.
Table: Histologic composition of bright spot sources
- © 2013 by American Heart Association, Inc.