Intraoperative near-infrared (NIR) fluorescence imaging is a novel technique that combines the use of a fluorescent agent with a dedicated near-infrared camera system, to allow real-time visualization of lymph nodes, tumor tissue and/or vital anatomic structures for surgical guidance (Vahrmeijer et al. 2013). NIR light ranges in the wavelength of 700-900 nanometers, is invisible to the naked eye and can only be detected with dedicated NIR imaging systems, which are currently available from various commercial companies. Fluorescent agents are mainly administered intravenously at a given time prior or during surgery, in order to enable realtime imaging during the procedure. The time of injection is dependent on the biodistribution of the specific agent. After injection the fluorescent agent is cleared by either the liver or kidneys and accumulates in the target (i.e. lymph node, tumor or vital structure) by either physiological processes (enhanced permeability and retention effect), specific targeting or through their clearance route.
A known challenge in the field of fluorescence guided surgery is the development of ideal NIR (tumor-targeted) fluorophores. Currently, the only clinically available NIR fluorophores are methylene blue (MB) and indocyanine green (ICG), both nonspecific dyes. Read more. . .