By the function of evaluating microcirculation and tissue viability, ICG fluorescence imaging has been used to quantify tissue perfusion in reconstructive surgeries and free flap tissue transplantations . It enabled the risk prediction of necrosis, achieving a reduction of complications due to the identifying inadequate perfusion, which is a significant signal of microcirculation insufficiency. In a multicentre phase II trial of ICG fluorescence imaging colorectal surgery with 504 patients (330 neoplastic cancers and 174 benign cancers) involved, ICG was administrated at two critical intraoperative time points. Firstly ICG was injected before bowel resection and images were acquired within 1 minute to assess the bowel perfusion, and the surgeons would adjust the transection point referring to whether the perfusion signal reaches the planned transection site. After construction of anastomosis, ICG was injected again for assessment of anastomotic vascular sufficiency, and anastomosis would be redone if the perfusion proved to be insufficient. With the assistance of ICG imaging, the anastomotic leak rate was decreased from 5.8% to 2.6%, and no anastomotic leaks was found during the 29 patients whose surgical plans were revised based on ICG intraoperative perfusion assessment . The result was also revealed in a multi-institutional study conducted in 2014, in which ICG fluorescence imaging was used to assess colon and rectal perfusion during colorectal resection. 11 out of 147 patients had the transection site altered and no anastomotic leaks appeared among them .