Fluorescence-guided surgery is an intraoperative optical imaging method that provides surgeons with real-time guidance for the identification and delineation of tumours or vital structures.
After the administration of a near-infrared dye or fluorophore, exogenous NIRF imaging can be obtained using imaging systems which are sensitive to invisible NIR light spectrum wavelengths of 700 to 900nm. The NIR light wavelength largely determines the degree of penetration of photons into the tissue. In the visible light range, photons have a depth penetration limited to a few millimeters and are suitable to detect superficial targets. However, photons in the NIR range can penetrate up to approximately a centimeter through tissue, which also allows for the detection of targets below the tissue surface.
NIR fluorophores enhance tissue-specific visualization and contrast it with surrounding tissues. Examples include the delineation of vital anatomical structures in relation to their adjacent structures and tumor delineation of healthy tissue. The fluorescence signal can either be visualized directly on the operating field or can be captured through dedicated cameras and displayed on the screen.
Intraoperative NIRF imaging relies on the availability of an intraoperative imaging system and a contrast agent to visualize the target structure/organ during surgery. The basic components of a fluorescence imaging system are (I) an NIR light source, (II) an NIR camera, (III) optics and filters, (IV) instrument control, acquisition and imaging software, and (V) computer, input and imaging hardware.
The most popular current clinical applications in surgery worldwide include fluorescence cholangiography, lymph node identification, real-time detection of cancerous tumors and assessment of tissue perfusion. In addition, fluorescence can also be used for, amongst others, the detection of (the course of) the ureters, the urethra, parathyroid glands and foci of endometriosis.