Narrative review of fluorescence imaging-guided liver surgery

: Indocyanine green (ICG) fluorescence imaging has come to be applied to hepatobiliary surgery not only visualization of bile duct but also for identification of subcapsular hepatic tumors and segmental boundaries. A large proportion of ICG molecules bind to high molecular-weight proteins such as albumin. ICG is selectively taken up to hepatocytes and excreted in the bile by an active transporter. Fusion ICG fluorescence images are obtained using a complementary metal-oxide semiconductor camera head and a near-infrared laser diode for ICG excitation. This method is helpful especially in cases of laparoscopic hepatectomy, wherein there is limited visual inspection and palpation in comparison with open surgery. ICG cholangiography is effective for visualizing the confluence of the left and right hepatic duct, decreasing the potential risks of bile duct stenosis or injury. ICG fluorescence imaging is also useful for the visualization of hepatic segment boundaries, which helps navigate the transection line in real time during hepatectomy. However, in the case of liver cirrhosis, the function of liver cells is depressed, and longtime ICG remains in the lesions; thus, the disappearance of fluorescence is delayed. ICG fluorescence imaging is a simple technology with the potential to improve the safety and quality of open, laparoscopic, and robotic hepatectomy.