Optimizing the image of fluorescence cholangiography using ICG: a systematic review and ex vivo experiments

Abstract

BackgroundThough often only briefly described in the literature, there are clearly factors that have an influence on the fluorescence intensity, and thereby the usefulness of the technique. This article aims to provide an overview of the factors influencing the fluorescence intensity of fluorescence imaging with Indocyanine green, primarily focussed on NIRF guided cholangiography.MethodsA systematic search was conducted to gain an overview of currently used methods in NIRF imaging in laparoscopic cholecystectomies. Relevant literature was searched to gain advice on what methods to use. Ex vivo experiments were performed to assess various factors that influence fluorescence intensity and whether the found clinical advices can be confirmed.ResultsICG is currently the most widely applied fluorescent dye. Optimal ICG concentration lies between 0.00195 and 0.025 mg/ml, and this dose should be given as early as achievable—but maximum 24 h—before surgery. When holding the laparoscope closer and perpendicular to the dye, the signal is most intense. In patients with a higher BMI and/or cholecystitis, fluorescence intensity is lower, but NIRF seems to be more helpful. There are differences between various marketed fluorescence systems. Also, no uniform method to assess fluorescence intensity is available yet.ConclusionsThis study identified and discussed several factors that influence the signal of fluorescence cholangiography. These factors should be taken into account when using NIRF cholangiography. Also, surgeons should be aware of new dyes and clinical systems, in order to benefit most from the potential of NIRF imaging.Electronic supplementary materialThe online version of this article (10.1007/s00464-018-6233-x) contains supplementary material, which is available to authorized users.

Optimizing Indocyanine Green Fluorescence Angiography in Reconstructive Flap Surgery: A Systematic Review and Ex Vivo Experiments

“…Another possible limitation is revealed by the observation of lower fluorescence intensity with higher doses of ICG. This phenomenon was also observed by van den Bos et al 19 Since the concentrations of ICG were diluted within 40 mg/mL of albumin in 0.9% NaCl dilution and lower concentrations were obtained by adding 40 mg/mL solution, it is possible that the absolute quantity of albumin is higher in lower concentrations of ICG. Therefore, an optimum dose cannot be given based on these ex vivo experiments.…”

“…The methods for these ex vivo experiments have been previously reported using a laparoscopic NIRF imaging device with special emphasis on cholangiography. 19 In this study, these experiments were reproduced using a handheld imaging device with special emphasis on angiography; additionally, statistical analyses have been performed. Associations between dosage of ICG, working distance, angle, penetration depth, and ambient light, and fluorescence intensity have been quantified.…”

“…However, consistent with van den Bos et al, the authors conclude that applying a weight-adjusted dose seems preferable over a fixed dose. 19 With regard to working distance and ambient light, a minority of studies reported the importance of this factor. Moyer et al previously described that fluorescence intensity, emitted by ICG, can be dependent on the distance from the camera to the skin and ambient light in the room without reporting the relation between these factors.…”

“…The methods for the ex vivo experiments have been previously reported by 2 of the authors (JVDB and FPW), using a laparoscopic NIRF imaging system. 19 In this study, a handheld NIRF camera (Fluobeam, Fluoptics, Grenoble, France) was applied, provided with integrated near-infrared light source with excitation between 750 and 800 nm and maximum fluorescein emission detection between 780 nm and 850 nm. In the author's institution, this system is used in daily practice for perioperative tissue perfusion evaluation as well as for mapping of lymphatic collecting vessels in the outpatient clinic.…”

“…5 This is important because ICG dosage influences fluorescence intensity, thereby influencing the adequacy of perfusion assessment. 19 On top of that, there are other factors that can have an impact on fluorescence intensity within the collected images, including the distance and angle between the camera and region of interest, and ambient light during perfusion evaluation. These are either not considered to be important or only briefly described in current literature.…”