A nurse and the attending physician continuously monitored the vital signs during the procedure and for one hour following the procedure. Percutaneous except RFA was performed by one of the attending physicians with 3-10 years experience in RFA and these procedures were mostly done under sonographic guidance and monitoring, except for three metastases that were not visualized on a sonographic examination and so they were treated under CT guidance. RFA was performed using a 500-KHz monopolar RF generator (either a CC-1, Integra Radionics, Burlington, MA or a multi-channel RF generator, Taewoong, Koyang, Korea). A single cool tip electrode (Cool Tip Electrode; Valleylab, Boulder, CO) or a clustered electrode (Valleylab) was used based on the target tumor size.

A single cool tip electrode was used for tumors smaller than 3 cm and a clustered electrode was used for tumors larger than 3 cm. Radiofrequency was initially applied for 12 minutes and for subsequent ablations for 6 to 12 minutes. An impedance-controlled automated pulsed RF algorithm was used (upper limit, 80 ohms) with a maximum peak current of 1000-2000 mA and 50-200 W. A peristaltic pump (Watson-Marlow, Paris, France) was used for cooling of the electrode with saline solution (0��) at a rate that was sufficient to maintain an electrode temperature below 20��. Constant monitoring of the temperature at the tip of the needle was also performed. After ablation, the electrode was withdrawn with cauterizing the tract. Treatment Assessment and Follow Up Immediately after the completion of the radiofrequency ablation procedure, a three-phase dynamic enhanced CT study (120 kVp, 200 mAs, 1.

5 ml/body weight of nonionic contrast) was performed to evaluate the presence of residual tumor at the treated site and any immediate complications such as hemorrhage and bowel injury. A lack of enhancement of the ablated zone that covered the tumor area with no evidence of irregular peripheral enhancement was considered complete ablation of the macroscopic tumor and a technically successful RFA procedure (Fig. 1). Four metastases were seen as residual lesions on the immediate post-RFA enhanced CT images and additional RFA treatment was performed within 24 hours after the initial RFA procedure. After additional sonography-guided or CT-guided RFA, technically successful RFA was performed for all of the treated lesions. Fig. 1 Imaging findings are shown for approximately 3.6 cm sized gastric cancer liver metastasis that was completely ablated (technical success) without recurrence. Initial follow-up imaging was performed within three months. Standardized time interval imaging was Brefeldin_A obtained at three and six months after the RFA procedure and then every six months.