| Summary: | Background: Safe values for quantitative perfusion parameters of indocyanine green (ICG) angiography have not been fully defined, and interpretation remains at the surgeon’s discretion. This prospective observational study aimed to establish the safe values for the quantitative perfusion parameters by comparing tissue oxygenation levels from HSI images in laparoscopic colorectal surgery. Methods: ICG angiography was performed using a laparoscopic near-infrared (NIR) camera system with ICG diluted in 10 mL of distilled water. For quantitative perfusion parameters, the changes in fluorescence intensity with perfusion times were analyzed to plot a time–fluorescence intensity graph. To assess real-time tissue oxygen saturation (StO<sub>2</sub>) in the colon, the TIVITA<sup>®</sup> Tissue System was utilized for hyperspectral imaging (HSI) acquisition. The StO<sub>2</sub> levels were compared with the quantitative perfusion parameters derived from ICG angiography at corresponding points to define the safe range of ICG parameters reflecting good tissue oxygenation. Results: In the regression analysis, T<sub>1/2MAX</sub>, T<sub>MAX</sub>, slope, and NIR perfusion index were correlated with tissue oxygen saturation. Using this regression model, the cutoff values of quantitative perfusion parameters were calculated as T<sub>1/2MAX</sub> ≤ 10 s, T<sub>MAX</sub> ≤ 30 s, slope ≥ 5, and NIR perfusion index ≥50, which best reflected colon StO<sub>2</sub> higher than 60%. Diagnostic values were analyzed to predict colon StO<sub>2</sub> of 60% or more, and the ICG perfusion parameters T<sub>1/2MAX</sub>, T<sub>MAX</sub>, and perfusion TR showed high sensitivity values of 97% or more, indicating their ability to correctly identify cases with acceptable StO<sub>2</sub>. Conclusion: The safe values for quantitative perfusion parameters derived from ICG angiography were T<sub>1/2MAX</sub> ≤ 10 s and T<sub>MAX</sub> ≤ 30 s, which were associated with colon tissue oxygenation levels higher than 60% in the laparoscopic colorectal surgery.
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