ResearchThermal tissue change induced by a microwave surgical instrument in a rat hepatectomy model

BackgroundMicrowaves exhibit great potential in tissue heating, which causes effective coagulation. Using this energy, we have developed the microwave coagulation surgical instrument (MWCX) for clinical application. Here, we characterized the impact of MWCX on tissues including heating property, tissue change, and spread of thermal injury.MethodsHepatectomy was performed with MWCX using a rat model. The resections were completed using various energy levels and powers. Tissue temperature during radiation was recorded. Tissue change and lateral thermal injury (LTI) was assessed immediately, 7 days, 3 months, and 6 months after resection.ResultsAll cutting and hemostasis procedures were successfully accomplished. Major histologic findings consisted of deformation or destruction of hepatocytes, tissue edema, and peripheral hemorrhage. At various energy levels, 200 to 1000 J, the tissue was heated up to approximately 80°C to 140°C causing 2.7- to 6.5-mm LTI on the 7th day. LTI was then decreased gradually in the following term. At certain energy levels, the application of neither 20 W nor 40 W induced significant difference in both heating and LTI.ConclusionsMWCX achieved effective tissue coagulation with relevant tissue injury, and it should be a good candidate for clinical application.