Feature Of The Week 8/31/14: Fully Integrated High-speed Intravascular OCT/NIRF Structural/Molecular Imaging In Vivo using a Clinically-available NIRF Emitting Indocyanine Green to Detect Inflamed Lipid-rich Atheromata in Coronary-sized Vessels
In current study, we fully integrated near-infrared fluorescence (NIRF) molecular imaging into intravascular OCT structural imaging. The OCT/NIRF single catheter imaging clearly demonstrated the microstructure of atheromata and simultaneously identified ICG-enhancing macrophage abundant lipid-rich areas of the plaques. Ex vivo NIRF imaging evidently validated in vivo OCT-NIRF imaging. NIRF signals on ex vivo fluorescence reflectance imaging colocalized well with in vivo NIRF imaging. In vitro ICG cell uptake, correlative fluorescence microscopy, and histopathology corroborated the in vivo imaging findings. Herein, our research team have solved the issues critical for application of this OCT/NIRF imaging technology to clinical practice.
In the first feasibility report of dual-modality frequency-domain optical coherence tomography (FD-OCT) and near-infrared fluorescence (NIRF) imaging to visualize both plaque structure and molecular pathway in vivo published in nature medicine 2011, there are important limitations to be addressed for clinical application, such as 1) slow pullback speed (2.5mm/sec) which requires proximal arterial occlusion to eliminate blood within imaging segment, 2) significant cross-talk between OCT and NIRF channels, and 3) nanobased NIRF agents as molecular signal enhancers which requires FDA approval for clinical use.
The present research enabled to offer 1) a high pull back speed (20 mm/s) enough for non-occlusive imaging just under contrast flushing within a few seconds, 2) minimize the cross-talk in double-clad fiber to a negligible level by innovation of the fiber-optic rotary junction (FRJ) design, 3) use indocyanine green (ICG) as a NIRF signal enhancing agent, which is an FDA-approved NIRF emitting agent clinically approved for fluorescence angiogram of humans in ophthalmologic and hepatologic imaging.
Our report shows important progress in intravascular imaging of high-risk coronary plaque which has a unique feature of inflamed thin-cap fibroatheroma. This novel imaging strategy is expected to offer a new avenue for accurate estimation of plaques prone to rupture in patients with coronary artery disease that may not be detected by any other conventional imaging modalities. In addition, we suggest that this novel strategy could have a far-reaching clinical use, and even facilitate new drug development.
For more information see recent Article. Courtesy of Jin Won Kim from Korea University Guro Hospital.