Indocyanine green enables near-infrared fluorescence imaging of lipid-rich, inflamed atherosclerotic plaques

Sci Transl Med. 2011 May 25;3(84):84ra45. doi: 10.1126/scitranslmed.3001577.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylation
  • Animals
  • Arteries / pathology*
  • Arteries / physiopathology
  • Capillary Permeability / physiology
  • Cattle
  • Diagnostic Imaging / methods*
  • Endocytosis
  • Fluorescence
  • Humans
  • Indocyanine Green*
  • Inflammation / complications
  • Inflammation / pathology*
  • Lipids / chemistry*
  • Lipoproteins, LDL / metabolism
  • Macrophages / metabolism
  • Macrophages / pathology
  • Plaque, Atherosclerotic / complications
  • Plaque, Atherosclerotic / diagnosis*
  • Plaque, Atherosclerotic / diagnostic imaging
  • Plaque, Atherosclerotic / physiopathology
  • Rabbits
  • Radiography
  • Serum Albumin, Bovine / metabolism
  • Spectroscopy, Near-Infrared / methods*

Substances

  • Lipids
  • Lipoproteins, LDL
  • Serum Albumin, Bovine
  • Indocyanine Green