A new system of microwave ablation at 2450 MHz : preliminary experience

The aim of this study was to assess the feasibility of the application of the new system (Emprint Microwave Ablation System, Covidien Boulder, CO, USA) and to identify its advantages. In particular the attention was focused to the spherical ablation zone obtained and its usefulness in terms of effectiveness. The new system is composed of: a 2450 MHz generator that delivers a maximum power of 100 W, a fiberglass antenna and a pump for internally cooled antenna. Ten liver nodules (8 hepatocellular carcinomas and 2 metastasis) were percutaneously treated (mean diameter 24.9 mm, range 16-35 mm). Technical success, ablation duration time, overall procedure time and safety were registered. To define the shape of the ablation zone, multiplanar reformatting (MPR) was performed. Roundness index transverse was calculated: a value near 1 represents a more spherical ablation zone shape, and a value distant from 1 implies an oval configuration. Technical success was 100 %. Mean ablation time was of 3.85 min (range 3-5 min), mean overall procedure time was 30.5 min (range 25-40 min). No major complications were recorded. Roundness index transverse presented a mean value of 0.94, meaning that a spherical shape of ablation zone was achieved. One of the most promising innovations of the new microwave technology is the spherical shape of the ablation volume that could be related with an improving of the effectiveness and safety.