**3.2 Technique of intraoperative RFA in different situations**

When performing intraoperative RFA some principal rules should be followed. IOUS guidance is mandatory for proper positioning of the RFA probe. A free-hand puncture technique usually allows more freedom to manipulate when compared to the puncture through guide, attached to the US-transducer. Mobilization of the liver is not mandatory but is sometimes necessary in order to achieve more comfortable positioning of the RFA electrode, to isolate the liver from adjacent organs/structures in order to protect them from

made for some patients with peritoneal carcinomatosis, if cytoreductive surgery plus intraperitoneal chemotherapy can be performed simultaneously with the liver-directed surgical treatment. In every case any attempt should be made initially for R0 resection even as a staged procedure. Survival rates following two-step hepatectomy for liver metastases still are better than those of combined RFA+liver resection procedures. RFA is recommended in some cases before portal vein embolisation to control small centrally placed lesion in the planned future liver remnant. When R0 hepatectomy deemed impossible RFA+resection can be considered. The aim of the procedure is to resect as much as possible of the lesions, treating smaller and centrally placed ones with RFA in order to preserve sufficient amount of residual healthy liver. However in patients with unresectable recurrence after liver resection, in high-risk patients with severe comorbidities or in those

refusing hepatic resection RFA is a treatment option as a sole procedure (Figure 4).

Fig. 4. Follow-up CT after intraoperative RFA of recurrent colorectal liver metastases after

In selected patients with synchronous bilobar metastases and resectable extrahepatic disease simultaneous RFA plus liver and extrahepatic resection can be safely performed (Julianov et al, 2004, 2006). A substantial survival advantage can be expected in patients in whom local control is achieved with RFA/RFA+resection, compared with those patients treated with chemotherapy only. In our study of patients with liver metastases there were no 2-year survivors between patients deemed unresectable at operation and further treated with chemotherapy only. For comparison - the 3-year survival rate for patients treated with liver resection alone was 71% vs. 34% for those treated with combined RFA+resection or RFA alone. However the mean number of liver metastases was 2.5 in the resection group vs. 5 in

When performing intraoperative RFA some principal rules should be followed. IOUS guidance is mandatory for proper positioning of the RFA probe. A free-hand puncture technique usually allows more freedom to manipulate when compared to the puncture through guide, attached to the US-transducer. Mobilization of the liver is not mandatory but is sometimes necessary in order to achieve more comfortable positioning of the RFA electrode, to isolate the liver from adjacent organs/structures in order to protect them from

previous resection (A), and of colorectal metastases in a high-risk patient (B) .

the combined treatment group (Julianov, 2009).

**3.2 Technique of intraoperative RFA in different situations** 

thermal injury, or for the purposes of outflow vascular control. The most deep and closest to the major vessel part of the lesion is treated first, to eliminate further cooling effect ("heat sink") of the blood flow on ablation process. During RFA we always apply Pringlemaneuver, starting at 5 minutes after beginning of each ablation cycle till its end. Finally the probe is cauterized before removing it from the liver, in order to minimize the risk of needle-tract seeding of viable tumor cells.

*RFA near major blood vessels.* Proximity of a major vessel was identified as an independent limiting factor for successful hepatic RFA (Mulier et al, 2005). In animal experiments with RFA a rim of viable tissue has been always observed around the large vessels >5mm (Lu et al, 2002). Thus vascular control becomes important adjunct to RFA procedure, when tumors near major vessels are treated in both normal and cirrhotic livers (Rossi et al, 2000; De Baere et al, 2002; Washburn et al, 2003). Pringle-maneuver is sufficient vascular control technique for lesions located near inflow vessels. However inflow occlusion does not eliminate the "heat sink" when the tumor located near major hepatic vein is treated. In this situation the backflow cooling from the hepatic vein can be simply controlled by finding with IOUS the respective vein confluence to the inferior vena cava, and compressing the vein with the transducer until its lumen disappears on IOUS-screen (Julianov, 2008, 2009). Even the lesions adjacent to the vena cava can be successfully treated if proper vascular control techniques are used during RFA (Julianov et al, 2008; Figure 3).

*RFA near hilar bile ducts.* RFA for a lesion near the hepatic hilum is considered dangerous because of the high risk from thermal injury and subsequent stricture of hilar bile ducts. However successful and safe RFA of a hepatic tumor near the hepatic hilum can be performed (Figure 5).

Fig. 5. Computed tomography of a patient with liver metastasis from gastrointestinal stromal tumor (A). RFA with cooling of bile ducts was performed (B).

For this purpose the left and right main duct should be protected. One option is to place the stents in both ducts through ERCP. Another option proven in both experimental and clinical setting is to cool the bile ducts during ablation. Our preferred option is to cool the biliary tree by perfusion of cold 5% isotonic glucose solution in the bile ducts using catheters inserted through small incision of the common bile duct, as proposed by D. Elias (Elias et al, 2001).

*Large-volume RFA.* For large lesions, more than a single positioning of the RFA probe is frequently necessary to control the tumor with appropriate safety margin. In such cases it is important to plan the whole RFA procedure with all positions of the electrode before starting the ablation. RFA causes changes in the coagulated liver parenchyma, which will affect further proper positioning of the probe under US-guidance (Figure 6). The geometry of overlapping ablations can vary widely, and they should be planned with respect of the size of the target lesion. A well-designed protocol for RFA of larger lesions should be used in order to ensure high success rate of complete ablation (Chen et al, 2004).

Fig. 6. IOUS images. Isoechoic liver metastasis with hypoechoic rim before treatment (A). The lesion is punctured with the LeVeen needle electrode and ablation started (B). The RFA cycle is finished (C).

To date the physiologic response of large-volume RFA (Figure 7), has not reported to be different from the more limited "usual" ablation volumes in clinical practice. However the safety limit of clinical RFA of the liver remains unknown.

Fig. 7. Computed tomography of a patient with colorectal liver metastases before (A) and one week after large-volume RFA (B). Posttreatment follow-up CT of a patient two weeks (C) and 6 months (D) after large volume RFA.

In animal model of RFA a 40% of the liver volume is ablated without mortality in healthy livers whereas in cirrhotic liver up to 20% can be ablated safely, without significant systemic inflammatory response (Ng et al, 2006). It is not clear whether these data are applicable in clinical setting. In our experience, the posttreatment course of patients with even very large volumes of hepatic RFA does not show any specific difference from more "usual" cases.
