Indocyanine Green-Enhanced Fluorescence-Guided Surgery: Lymphatic Navigation, Perfusion Evaluation and Future Perspectives

Abstract

Indocyanine green (ICG) is the most commonly used fluorophore in fluorescence imaging. It is a water-soluble, tricarbocyanine dye that binds to blood lipoproteins and remains confined in the intravascular compartment until elimination. It is selectively taken up by hepatocytes and excreted into the bile. This fluorophore has tissue penetration up to 5 mm and a plasma half-life of 3-5 min with biliary excretion after 15-20 min, thus it is ideal for repeated applications [1].ICG has several clinically excellent properties, which have been thoroughly verified during its long clinical use: (1) it is nontoxic and nonionizing and therefore has a good patient safety profile; (2) it binds efficiently to blood lipoproteins and does not leak from the circulation, which makes it ideal for angiography; (3) it has a short life-time in the blood circulation, allowing for repeated applications; (4) it offers a good signal-to-noise ratio since separate wavelengths are used for illumination and recording so that only the target, not the background, is visible; (5) it operates in tissue optical window (near infrared) so it provides deep imaging; (6) it is used with simple and cheap imaging devices.