Intraoperative biliary anatomy visualization using indocyanine green fluorescence micro-dosing: a quantitative preclinical study.

BACKGROUND: The critical view of safety aims to reduce bile duct injury during laparoscopic cholecystectomy. Near-infrared (NIR) fluorescence cholangiography with indocyanine green (ICG) may enhance visualization of extrahepatic biliary anatomy, but conventional dosing can increase hepatic background fluorescence and optimal weight-adjusted strategies remain unclear. This study quantitatively evaluated weight-adjusted systemic ICG regimens within a predefined micro-dose domain and assessed the temporal stability of bile duct-to-liver fluorescence contrast within an operative time window. METHODS: Ten pigs received a single randomized intravenous injection of ICG at one of five weight-adjusted doses (0.000625, 0.004, 0.01, 0.025, or 0.05 mg/kg). NIR fluorescence imaging was performed at 30, 60, and 90 min using a standardized laparoscopic platform in overlay mode. Extrahepatic bile ducts and hepatic parenchyma were manually segmented in Computer Vision Annotation Tool to generate masks. Pixel-wise intensity extraction was aggregated to obtain one bile duct-to-liver contrast ratio per animal per time point. Data were analyzed using a linear mixed-effects model with animal as a random effect. RESULTS: Fluorescence was detectable in all animals from 30 to 90 min across all dose regimens. When doses were grouped into a predefined micro-dose domain (≤ 0.01 mg/kg; n = 6 animals) versus higher doses (≥ 0.025 mg/kg; n = 4 animals), mixed-effects modeling showed a main effect of dose group (F(1,8) = 6.539, p = 0.034), with consistently higher estimated marginal mean contrast ratios in the micro-dose domain (ΔEMM = 2.350 ratio units, 95%CI 0.549-4.152). No significant effect of time was observed (F(2,18) = 0.824, p = 0.455) within the 30-90 min window evaluated. CONCLUSIONS: Systemic weight-adjusted micro-dose ICG administration provided higher bile duct-to-liver contrast in a preclinical model within the operative window evaluated. These findings support further investigation of standardized micro-dose protocols and quantitative fluorescence-guided strategies in clinical settings.