# Laparoscopic Microwave Ablation: Which Technologies Improve the Results
## 4 LUS Evaluation
The access of the LUS probe into the peritoneal cavity is conditioned by the position of the trocars: first, the umbilical port can be chosen for laparoscopic exploration by the camera, and the second trocar for the LUS access could be decided on the information obtained both the preoperative imaging evaluation and the intraoperative conditions as established by laparoscopy visualization. LUS examination of the liver can be usually accomplished with a direct contact technique in the presence of the natural humidity of the liver surface, which permits an excellent acoustic touch with the transducer. However, for lesions at the hepatic dome or localized in the posterior segments, contact between the transducer and liver surface may be limited: in this case, the saline solution can be introduced between the liver and diaphragm thus creating an acoustic window that allows you to view these areas without air interference (water-immersion method). If, however, this is not sufficient, it is possible to decrease the pneumoperitoneum to 6-8 mm thus reducing the angle of contact with the hepatic surface, thus improving the ultrasound image. With these devices, it is also possible during laparoscopy as with open surgery to completely examine the liver with the ultrasound probe to identify nodules, their size, characteristics and their exact location according to the Couinaud classification of liver anatomy [39]. After the lesions have been localized, the antenna for a microwave ablation (MWA) (or electrode needle for radiofrequency ablation (RFA)) can be accurately inserted into the nodule. When it is necessary to treat lesions localized in segment 1 or in the posterior segments, a longer laparoscopic antenna could be required (27-30 cm). The antenna proceeds through the abdominal wall and the pneumoperitoneum space prior to reaching the liver surface: this space could increase the difficulties in the movements of the tip of the antenna. In fact, laparoscopic ablation is more technically difficult than percutaneous procedure due to a different three-dimensional spatial plan, decreased liberty in antenna angulation and introduction, and with the free-hand guide of intraoperative ultrasound (IOUS) [40]. Other laparoscopic probes have been equipped with a pore for a guide to insert the antenna: however, the rigid direction line due to the pore prevents the possibility of guiding the antenna into lesions located in different sites of the liver [41]. A LUS-guided interventional procedure [42] can be successfully accomplished if the following ideal conditions are satisfied: (1) a good visualization of the lesion is necessary: the ultrasound probe must be positioned on the liver surface to show the largest diameter of the whole nodule; (2) the antenna must be inserted as close as possible to the transducer of the ultrasound probe trying to have an angle oblique to it so that you can follow the path of the antenna tip as closely as possible with the ultrasound. Once the antenna has been inserted, with delicate rotational movements of the probe on its axis, it must follow the path of it up to the lesion. Being a totally free-hand technique, it is possible that the first attempt will not be adequate: in this case, based on the position of the antenna with respect to the nodule, it is extracted by repositioning it at a different point on the liver surface, taking into account that small distances on the surface of the liver can result in much wider distances within the liver, especially if the nodule is very deep. For lesions located in the posterior segments, it is necessary to introduce the antenna on the liver surface distant from the lesion: in this case, the transducer cannot contemporaneously display the nodule and the antenna tip. A technical variant is the IHVO.