Clinical applications of fluorescence imaging in hepatobiliary and pancreatic surgery

Intraoperative fluorescence imaging  has become used widely for real-time visualization of biological structures and assessment of blood perfusion. In hepatobiliary and pancreatic surgery, fluorescence imaging using indocyanine green can be applied in the following four applications.

1. Fluorescence cholangiography: fluorescence images of the extrahepatic bile ducts can be obtained by intrabiliary injection of ICG solution (0.025 mg/mL) or preoperative intravenous injection (IV) of ICG (2.5 mg). The latter technique begins to be used worldwide for confirmation of the bile duct anatomy during minimally-invasive cholecystectomy.
2. Identification of hepatic tumors: IV-injected ICG (0.5 mg/kg) accumulates in hepatocellular carcinoma tissues and in non-cancerous hepatic parenchyma surrounding liver metastasis, which can be used for intraoperative identification of subcapsular hepatic tumors by fluorescence imaging.
3. Hepatic segmentation: ICG solution (0.25 mg in 5 mL indigo-carmine solution) is injected into a tumor-bearing portal branch under ultrasound guidance (positive staining technique). ICG can also be administered intravenously following closure of a corresponding portal pedicle (negative staining technique). These techniques enable long-lasting delineations of segmental boundaries throughout hepatectomy procedures because ICG retains in hepatocytes for more than 5 hours.
4. Assessment of blood perfusion: fluorescence imaging following intraoperative bolus IV ICG (2.5mg) visualizes arterial/portal blood flows and perfusions to the surrounding organs during surgeries with resection/reconstruction of major vessels.

These techniques will develop into an indispensable intraoperative navigation tools, which may enhance accuracy of hepatobiliary and pancreatic surgery especially  in the minimally-invasive setting.