Indocyanine green(ICG) has been used to estimate cardiac output and liver function. Protein-bound ICG was found to emit fluorescence, peaking at about 840 nm, under illumination with near-infrared light (750−810 nm). Because little light at 840 nm is absorbed by hemoglobin or water, fluorescence signals emitted by protein-bound ICG can be visualized through connective tissue 5−10 mm thick.
ICG-fluorescence imaging is useful for hepatobiliary surgery because most of injected ICG is metabolized in the liver and secreted into bile. And so, bile duct can be visualized with near-infrared light illumination.
Secondly, segment identification is important for the anatomic liver resection. Ischemic demarcation or indigo-carmine staining is often unclear. But ICG Fluorescence imaging is already clear.
For segmentation, ICG can be directly injected into portal vein or systemically after the clamping of the portal pedicle (negative staining).
Thirdly, ICG-fluorescence imaging is useful for the detection of the liver tumor.
In hepatocellular carcinoma tissue, the biliary excretion of ICG in the tumor is impaired and ICG is retained in the HCC tissue for several days. In metastatic cancer, fluorescence can be found in the rim of the tumor.
Recently, laparoscopic fluorescence imaging system is commercially available and this system is applied in the pure laparoscopic liver resection for the segmentation, tumor detection and bile duct division.
In our center, ICG-fluorescence imaging is routinely used in pure laparoscopic donor hepatectomy. In donor right hepatectomy, the right hepatic artery (RHA) and right portal vein (RPV) were identified, and vessel loops were placed around them. The RHA and RPV were temporarily clamped using laparoscopic bulldog clamps. ICG was injected intravenously, and the exact midplane of the liver was demarcated using a near-infrared camera. After parenchymal dissection, the bile duct was illuminated with ICG-fluorescence imaging. This can show the exact anatomy of the right and left hepatic duct and so we can easily identify the division point without injury to left hepatic duct.

ICG-fluorescence imaging would be a mandatory equipment for the detection of the tumor, segmentation and identification of the bile duct.