Research ArticleAtherosclerosis

Indocyanine Green Enables Near-Infrared Fluorescence Imaging of Lipid-Rich, Inflamed Atherosclerotic Plaques

Science Translational Medicine  25 May 2011:
Vol. 3, Issue 84, pp. 84ra45
DOI: 10.1126/scitranslmed.3001577

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Abstract

New high-resolution molecular and structural imaging strategies are needed to visualize high-risk plaques that are likely to cause acute myocardial infarction, because current diagnostic methods do not reliably identify at-risk subjects. Although molecular imaging agents are available for low-resolution detection of atherosclerosis in large arteries, a lack of imaging agents coupled to high-resolution modalities has limited molecular imaging of atherosclerosis in the smaller coronary arteries. Here, we have demonstrated that indocyanine green (ICG), a Food and Drug Administration–approved near-infrared fluorescence (NIRF)–emitting compound, targets atheromas within 20 min of injection and provides sufficient signal enhancement for in vivo detection of lipid-rich, inflamed, coronary-sized plaques in atherosclerotic rabbits. In vivo NIRF sensing was achieved with an intravascular wire in the aorta, a vessel of comparable caliber to human coronary arteries. Ex vivo fluorescence reflectance imaging showed high plaque target-to-background ratios in atheroma-bearing rabbits injected with ICG compared to atheroma-bearing rabbits injected with saline. In vitro studies using human macrophages established that ICG preferentially targets lipid-loaded macrophages. In an early clinical study of human atheroma specimens from four patients, we found that ICG colocalized with plaque macrophages and lipids. The atheroma-targeting capability of ICG has the potential to accelerate the clinical development of NIRF molecular imaging of high-risk plaques in humans.

Footnotes

  • Citation: C. Vinegoni, I. Botnaru, E. Aikawa, M. A. Calfon, Y. Iwamoto, E. J. Folco, V. Ntziachristos, R. Weissleder, P. Libby, F. A. Jaffer, Indocyanine Green Enables Near-Infrared Fluorescence Imaging of Lipid-Rich, Inflamed Atherosclerotic Plaques. Sci. Transl. Med. 3, 84ra45 (2011).

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