Microwave and radiofrequency systems

The microwave unit (ECO-100E, Eco Medical) consisted of a microwave generator, a flexible coaxial cable, a water-pumping machine and a needle antenna with two lumens in the shaft to circulate the cooling water (8). The microwave irradiation frequency was 2450 MHz. The output powers could be modulated from 10 to 100 W. The 2 mm long irradiating segment was embedded in the front of the needle antenna and 11 mm away from the shaft tip. The socket at the end of the needle antenna was used to connect the plug of the cable coming from the microwave generator.

All of the RFA procedures in this study were performed with a 480 KHz radiofrequency generator (S-5L, MedSphere International) that provided a maximum power output of 50 W. Radiofrequency energy was deposited by using an internally cooled applicator with a cool-tip single-needle electrode. When the generator is operated in automatically pulsed mode according to the manufacturer’s recommendations during ablation, the output is controlled by an algorithm with an impedance feedback loop that is used to maximize energy delivery by minimizing charring. The electrode shaft was a 16-gauge monopolar electrode with two lumens that enabled internal fluid circulation and active stainless steel tip exposure of 2 cm.