Objective: Causing the different ablation results at the same power output or net power output, but the same applied tissue power can create the same ablation results. Calculating this value is the focus of research, which could provide accurate reference basis.

Methods: We took two methods (water special heat capacity measurement and bio-heat transfer equation solution) to calculate the applied tissue power when power outputs were 40W, 60W and 80W. The first one is through measuring the raising temperature of water to calculate at thermal isolation environment. The other one is to calculate by bio-heat transfer equation according to the transient variation of temperature.

Results: When power outputs were 40W, 60W and 80W, the net power outputs were 39.4W, 57.5W and 74.7W by power instrument. The applied tissue powers were 32.2W, 46.6W and 58.5W by the method of special heat capacity; by the other method, the applied tissue powers were 29.2W, 41.3W and 47.7W. Thus, we built the numerical relationship between the net power output and the applied tissue power to calculate applied tissue power efficiently. Meanwhile, this fitting equations are true by comparing applied tissue power through fitting equation with that calculated by the two methods at 70W power output.

Conclusion: Compared two fitting equations, the one by the method of bio-heat transfer equation is more suitable and has less error to calculate. And applied tissue power is an important reasonable reference to assist clinical guidance, which avoids the loss power to cause different and error results.