Kinetics analysis of indocyanine green based on a novel mouse model for distinguish between tumor and inflammation

Near-infrared (NIR) imaging with indocyanine green (ICG) has been proved feasible for the visualization of tumor and enable real-time guidance during tumor resection. However, ICG is a non-receptor specific NIR dye that accumulates in other hyperpermeable tissues such as inflammatory tissue. In this study, we found visible difference between tumor and inflammation in 6 oral cancer patients on NIR images after 24 hours of 0.75 mg/kg ICG injection. In order to obtain optimal ICG dose and observation time for better discrimination effect, we constructed the sponge implant model of angiogenesis and subcutaneous tumor model in the same C3H mice for further study. This mouse model was first proved feasibility for ICG NIR imaging and difference between tumor and inflammation was successfully acquired in the model. Studies on this model avoid the interference of individual differences between tumor and inflammation and revealed the causal relationship between tissue permeability and fluorescence. The difference of ICG kinetics between tumor and inflammation tissues was studied based on this mouse model. Results showed that tumor-to-inflammation ratio (TIR) of fluorescence intensity was dose independent and increased with time, indicating that more ICG leakage and less clearance in tumors may lead to brighter NIR imaging than in inflammations. Thus, we recommended higher ICG injection dose and longer observation time in order to better differentiate between tumor and inflammation by NIR imaging.