Oppermann 2022: Continous organ perfusion monitoring using indocyanine green in a piglet model
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Background: 
‍Unrecognized organ hypoperfusion may cause major postoperative complications with detrimental effects for the patient. The use of Indocyanine Green (ICG) to detect organ hypoperfusion is emerging but the optimal methodology is still uncertain. The purpose of this study was to determine the feasibility of real-time continuous quantitative perfusion assessment with Indocyanine Green (ICG) to monitor organ perfusion during minimally invasive surgery using a novel ICG dosing regimen and quantification software. 

Method: 
‍In this experimental porcine study, twelve subjects were administered a priming dose of ICG, followed by a regimen of high-frequency (1 dose per minute), low-dose bolus injections with weight-adjusted (0.008 mg/kg) ICG allowing for continuous perfusion monitoring. In each pig, one randomly assigned organ of interest [stomach (n = 3), ascending colon (n = 3), rectum (n = 3) and spleen (n = 3)] was investigated with varying camera conditions. Video recording was performed with the 1588 AIM Stryker camera platform and subsequent quantitative analysis of the ICG signal were performed usinga research version of a commercially available surgical real-time analysis software.
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Results: 
‍Using a high-frequency, low-dose bolus ICG regimen, fluorescence visualization and quantification in abdominal organs were successful in the stomach (3/3), ascending colon (1/3), rectum (2/3), and the spleen (3/3). ICG accumulation in the tissue over time did not affect the quantification process. Considerable variation in fluorescence signal was observed between organs and between the same organ in different subjects. Of the different camera conditions investigated, the highestsignal was achieved when the camera was placed 7.5 cm from the target organ.

Conclusion:
‍This proof-of-concept study finds that real-time continuous perfusion monitoring in different abdominal organs using ICG is feasible. However, the study also finds a large variation in fluorescence intensity between organs and between the same organ in different subjects while using a fixed weight-adjusted dosing regimen using the same camera setting and placement.

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Hayami 2019: Visualization and quantification of anastomotic perfusion in colorectal surgery usingnear infrared fluorescence Conclusions:
Perfusion of the anastomosis couldbe successfully visualized and quantified using NIRF imaging with ICG. T0 might be a useful parameter for prediction of AL.

Background:
Anastomotic leakage (AL) is one ofthe most troublesome complications in colorectal surgery. Recently, nearinfrared fluorescence (NIRF) imaging hasbeen used intraoperatively to detect sentinel lymph nodes and visualize theblood supply at the region of interest (ROI). The aim of this study was toevaluate the role of visualization and quantification of bowel perfusion aroundthe anastomosis using NIRF system in predicting AL.
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Methods:
A prospective study was conductedon patients who had laparoscopic surgery for colorectal cancer at ourinstitution. Perfusion of the anastomosis was evaluated with NIRF imaging afterintravenous injection of indocyanine green (ICG). The time course of fluorescenceintensity was recorded by an imaging analyzer We measured the time from ICGinjection to the beginning of fluorescence (T0), maximum intensity (Imax), timeto reach Imax (Tmax), time to reach Imax 50% ( Tmax 1⁄2 ) and slope (S) after theanastomosis.
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Results:
Tumor locations were as follows; cecum:2, ascending colon: 2, transverse colon: 7, descending colon: 1, sigmoid colon:2, rectosigmoid colon: 3 and rectum: 6 (one case with synchronous cancer). Alloperations were performed laparoscopically. Four patients were diagnosed withor suspected to have AL (2 patients with grade B anastomotic leakage after lowanterior resection, 1 patient with minor leakage in transverse colon resectionand 1 patient needing re-anastomosis intraoperatively in transverse colon resection).T0 was significantly longer in the AL group than in patients without AL (64.3 ±27.6 and 18.2 ± 6.6 s, p = 2.2 × 10−3).

Wada 2017: ICG Fluorescence Imaging for Quantitative Evaluation of Colonic Perfusion in Laparoscopic Colorectal Surgery
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Conclusions:
‍ICG fluorescence imaging is usefulfor assessing anastomotic perfusion in colorectal surgery, which can result inmore precise operative decisions tailored for an individual patient.

‍Background:
‍Fluorescence technology withindocyanine green (ICG) provides a real-time assessment of intestinalperfusion. However, a subjective evaluation of fluorescence intensity based onthe surgeon’s visual judgement is a major limitation. This study evaluated thequantitative assessment of ICG fluorescence imaging in determining thetransection line of the proximal colon during laparoscopic colorectal surgery.
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Methods:
‍This is a retrospective analysis of a prospectively maintained database of 112 patients who underwent laparoscopic surgery for left-sided colorectal cancers.After distal transection of the bowel, the specimen was extractedextracorporeally and then the proximal colon was divided within thewell-perfused area based on the ICG fluorescence imaging. We evaluated whetherquantitative assessment of intestinal perfusion by measuring ICG intensitycould predict postoperative outcomes: Fmax, Tmax, T1/2, and Slope were calculated.Results Anastomotic leakage (AL) occurred in 5 cases (4.5%). Based on the fluorescenceimaging, the surgical team opted for further proximal change of the transectionline up to an “adequate” fluorescent portion in 18 cases (16.1%). Among the 18patients, AL occurred in 4 patients (4/18: 22.2%), whereas it occurred in only1 case (1/94: 1.0%) in the good perfusion patients who did not need proximalchange of the transection line. The Fmax of the AL group was less than 52.0 inall 5 cases (5/5), whereas that of the non-AL group was in only 8 cases(8/107): with an Fmax cutoff value of 52.0, the sensitivity andspecificity for the prediction of AL were 100 and 92.5%, respectively.Regarding postoperative bowel movement recovery, the Tmax of the early flatus group or earlydefecation group was significantly lower than that of the late flatus group orlate defecation group, respectively.