**9. Key points**

Starting from the use of IOUS, Torzilli introduces new types of resection, such as mini-mesohepatectomy, for tumor formations located at the confluence of the cave vein with superhepatic veins [11, 12, 111]. These resections are based on the ultrasound study of the relationship between the tumor and the suprahepatic veins and the analysis of the blood flow at this level after clamping the proposed vein for resection. Evidence of an inverse flow in the peripheral portion of the compressed vein or of a collateral shunt between the clamped vein and the other superhepatic vein or cava vein will allow the ligation and segregation of the tumoraffected suprahepatic vein and the achievement of a limited resection, while maintaining the

Summarizing, the use of IOUS allows the extension of surgical indications for certain liver

IOUS is still characterized by several drawbacks: it cannot detect lesions smaller than 3 mm, its accuracy is dependent on the surgeon's skill and experience, the images are 2D and there is a "blind area "of about 1 cm below the surface of the liver, which is particularly problematic in the case of small hepatic metastases due to colorectal cancer that are mainly located on the surface of the liver. Of course, associating contrast agents has greatly improved IOUS accuracy; however, the disadvantage of visualization of the lesions for a too short period of time makes this technique to be of limited applicability in guiding hepatic resections that may last

Recently, a new fluorescent approach, using indocyanine green (ICG), has been proposed to improve the intraoperative detection of neoplastic lesions [113, 114]. ICG is a non-specific molecule that allows detection of tumor tissue, but with limited specificity. The main advantage of its use is its safety and its commercial availability as a contrast substance. The imaging technique of intraoperative fluorescence using ICG was initially used for the detection of sentinel lymph nodes in patients with gastric, colon, and breast cancer [115, 116]. Several studies have shown that malign liver tumors show strong fluorescence when preoperative ICG administration is made [117, 118]. This technique is based on the fact that ICG binds to plasma proteins and together emit light with a peak wavelength of approximately 830 nm

Initially, ICG-fluorescence imaging was limited to open surgery alone. After year 2010, as laparoscopic and robotic imaging systems with fluorescence have developed, ICG-fluorescence imaging has been extended to minimally invasive abdominal surgery, especially for the visualization of extrahepatic biliary tract anatomy (during laparoscopic/robotic cholecystectomies) [120], an approach known as fluorescence cholangiography [121]. In 2014, the use of ICG-fluorescence imaging was reported for the identification of subcapsular hepatic tumors before liver transection [122]. A new laparoscopic imaging system is starting to be used, this system overlapping pseudo-color fluorescence images with white color-light images in real-time (fusion ICG-fluorescence imaging) with the proposal to identify segmental hepatic margins and localization of liver tumors [123]. Thus, ICG has the ability to "label" bile ducts

lesions that were either considered unresectable or required major surgery [104].

principles of oncological radicality [11, 12].

when illuminated with infrared light [119].

**8. Future perspectives**

82 Liver Research and Clinical Management

between 2 and 6 h [112].

