Basic knowledge of a microwave tissue coagulator and its clinical applications

A microwave tissue coagulator originally developed to control hemorrhage during hepatic resection has recently found widespread use in the field of minimally invasive surgery. This surgical tool is based on the principle that by radiating a 2450-MHz (12-cm wavelength) microwave from a monopolar antenna within tissue, the heat generated will be limited to within the electromagnetic field generated around the antenna, leading to coagulation of protein in that field. It is therefore possible to use this monopolar antenna as a surgical electrode. The coagulation field is determined by the relationship between the wavelength frequency, tissue-specific permittivity, antenna length, waveform and output, and duration of the irradiation. Since this technique has been applied to devise a new method of hepatectomy, it has also found use in various other surgical fields, such as gastrointestinal tract endoscopic surgery, laparoscopic surgery, and percutaneous surgery. It has also enhanced therapeutic results, notably in cancer therapy.