Optimization of a Novel Microwave Tumor Ablation System in an in Vivo Porcine Liver Model

Background Radiofrequency (RF) ablation is commonly used in the treatment of surgically unresectable hepatic tumors. It is amenable to open, laparoscopic, or percutaneous application, it makes use of well-understood principles of electrical and thermal heating of tissue, and it is readily available. However, local recurrence rates following RF ablation are as high as 39%. Microwave (MW) ablation is a novel therapy that has several theoretical advantages over RF ablation, including a larger zone of active heating, higher temperatures, and the capacity for ablation with several, simultaneously active probes. Currently MW ablation is in clinical use in a number of Asian centers . However, more widespread adoption has been prevented by a relatively small lesion size, requiring as many as 46 overlapping ablations to treat a single tumor. This appears to be due to a high level of power reflected back from the liver, causing heating of the probe, cable, and generator and limiting duration of MW application to 30-90 seconds. Recently, advances in antenna design have led to a new MW ablation system in which power feedback is markedly reduced, allowing for longer times of application, greater power deposition, and larger ablation lesion sizes. This study was designed to determine the optimal parameters of this prototype microwave ablation system in an in vivo porcine liver model.