# Laparoscopic Microwave Ablation: Which Technologies Improve the Results
## 3 ICG Fluorescence Imaging  
In recent studies, indocyanine green (ICG) fluorescence seems to be a valid tool to increase the safety of liver resection. Some authors [28; 29] showed that LUS integrated with ICG fluorescence imaging permitted the identification of HCC nodules: in fact, the use of an LUS probe may be associated with difficulties in visualizing small subglissonean nodules which could be easily identified by ICG imaging. A single dose of ICG (generally 0.5 mg/kg) used for routine liver function tests (with the LiMON device) should be injected 24-36 h before the surgical procedure and it is sufficient to identify nodules using intraoperative fluorescence imaging. Detection of hepatic lesions by ICG fluorescence is determined by the distinction between the tumoral fluorescent aspect and the nonfluorescent remaining liver parenchyma.  
Usually, ICG dye is selectively absorbed by hepatocytes through two specific transmembrane transport systems: organic anion-transporting polypeptides (OATP) and sodium-taurocholateco-transporting polypeptides (NTCP). On the other hand, the ICG excretion into the bile ducts is mediated by the activity of canalicular transporters, called multidrug resistance-associated proteins (MRP), that are expressed in the apical part of the hepatocytes [30].  
* In this setting, ICG fluorescence imaging can be also used to obtain information on nodule characteristics and to help in targeting the lesion;
* LUS is a fundamental tool for laparoscopic ablation procedures, but it has some drawbacks and difficulties in interpreting images. ICG fluorescence imaging is a promising method for navigation surgery, which allows the limitations of ultrasound examination to be overcome, above all for the subglissonean nodules. In a minimally invasive setting, ICG fluorescence can substitute the tactile feedback of the hand in the presence of soft parenchyma and in some cases, permits the identification of small superficial nodules not identified by the preoperative imaging modalities, completing the LUS staging. In the presence of macronodular cirrhosis and irregular liver surface, it can overcome the LUS difficulties due to the inadequate contact with the liver parenchyma, in the detection of superficial nodules [31; 32; 33];
* ICG imaging is very fast and perfectly integrated into the surgical equipment because fluorescent images of hepatic nodules are visualized by simply fixing on the liver surface with the camera and switching the camera system to the near-infrared function;
* ICG fluorescence imaging could identify different patterns of fluorescence for HCC nodules according to their grade of differentiation [34]: intense and homogenous fluorescence is indicative of well-differentiated HCC, while moderate or poorly differentiated tumor generates partial or rim-type fluorescence;
* In some procedures used during the laparoscopic thermoablation (IHVO) [26], it is possible to evaluate the ischemic effect of the occlusion of the vessel feeding the lesion. In this case, the ICG injection is performed immediately after the ablation of the vascular pedicle, and it is possible to visualize the area of the liver surface without IGC fluorescence (Figure 5).  
However, this technology presents two major drawbacks. The first is the lack of penetration into the parenchyma (up to 8 mm from the liver surface), so, only superficial tumors can be visualized by this technique. On the second, ICG fluorescence could present a relatively high incidence of false-positive rate: benign nodules, biliary hamardmas and nodular hyperplasia can show a well-defined fluorescence [31; 35].