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A Review of Indocyanine Green Fluorescent Imaging in Surgery

Abstract
The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

1. Introduction
Fluorescence Imaging (FI) is one of the most popular imaging modes in biomedical sciences for the visualisation of cells and tissues both in vitro and in vivo [1]. The benefits of FI include high contrast, that is, signal to noise ratio (SNR): only the target, not background, is visible because separate wavelengths are used for illumination and recording (cf. Figure 4);


The principle of fluorescence imaging. The radiation from the light source is filtered by a high-pass filter, Fs, to remove the fluorescent wavelengths. The blood and ICG suspension under a tissue absorbs the excitation wavelengths and emits in fluorescent high sensitivity: extremely small concentrations can often be made visible; Gives molecular information: makes some (bio) chemistry spatially and temporally visible;great tools for research: several possible imaging modes, most of which are unique; cheap: the optical instrumentation and computing needed are quite simple;
easy to use: resembles classical staining.

Fluorescent imaging is a relatively recent imaging method and thus still developing in many ways. This is especially true for indocyanine green (ICG) imaging in its new clinical applications recently proposed in various branches of surgical medicine, although it has been used in some clinical applications routinely already for almost sixty years. Thus, ICG is well known in its established clinical applications, which greatly facilitates its introduction to new applications. From an engineering point of view, image and video processing seems to be among the main areas in which ICG imaging (ICGI) has potential for major developments, for example, for analysis of ICG fluorescence dynamics [2] (cf. Figure 2). This means, among other things, that a lot of computing development work is still needed for a broader acceptance of various emerging ICG-based medical imaging methods [3].

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3346977/