Simulation Research On Temperature-controlled Radiofrequency Ablation Of Human Liver

Radiofrequency ablation (RFA) has emerged as a new medical treatment approachof hepatic carcinoma，which has the dominant features of broad clinical indications,fewer complications, low costs, minimally invasive and controllable ablation area. Dueto the complexity of achieving precise ablation, computer simulation of RFA becomes ahotspot in this research field. It can promote the study on the mechanism of RFA andassist physicians to develop the surgical plans more suitable for patients, therebyimproving the efficacy and safety of RFA treatment.For simulations of RFA nowadays, most of the simulation models chose theregular geometric model which fails to reflect the real shape of liver. In addition, as forsimulation of temperature-controlled mode of RF power, they either oversimplified it orachieved it with complex realization that could not being well referred to. Therefore, thestudy has been carried out on the modeling of temperature-controlled RFA of liver thatwas based on the original abdominal CT images using Amira and COMSOL. Thespecific process was as follows. Firstly, a lifelike geometric liver model was constructedbased upon abdominal CT data of human. Then the simulation oftemperature-controlled RFA, which adjusted its applied voltage of electrode byfeedback temperature using the proportional-integral controlled algorithm, wasconducted based on the geometric liver model. After that, two different evaluationmethods (Isotherms and Arrhenius tissue damage coefficient) were utilized to assess theablation. At last, the impact factors on the ablation efficacy, such as the variable livertissue parameters and the ablation mode, were discussed systematically. The simulationresults show that the liver model can not only well reflect the real shape of liver, butalso suit to future physics modeling. When the temperature-controlled mode issimulated using PI control algorithms that based on feedback temperature, the tissuemaximum temperature and the applied voltage are compatible with the clinical ones,which means the simulation of temperature-controlled mode is satisfactory. When itcomes to the efficacy evaluation of ablation, the ablation area defined by Isotherms isuniformed and symmetrically distributed, with smooth contour; however, the ablationarea verified by Arrhenius tissue damage coefficient is roughly symmetry with roughcontour. The final ablation areas defined by IT60are significantly smaller than clinicalone; whereas ablation areas verified by IT50and D99are more consistent with clinical ones, each of them has its own merits in ablation evaluation. The long and short axes ofablation area using IT50are considerately compatible with clinical ones. Whereas in theablation area defined by D99, there are some holes that demonstrate incompletelyablation at moments, which indicates D99have certain superiority in predictingincompletely ablation. Then from the factor analysis of RFA efficacy, we can learn thatthe blood perfusion, which can significantly promote the development and final volumeof ablation, is the most influential tissue parameter in terms of ablation; whereas thespecific heat capacity has little influence on ablation when tissue parameters vary oneby one. The combined effects of various tissue parameters can not only promote thedevelopment of the ablation greatly, but also increase the final ablation volumesignificantly. Temperature-controlled mode can impact tissue maximum temperatureand resistive losses tremendously. Besides, it can significantly improve the efficiency ofablation when compared with the constant voltage mode.In conclusion, the geometric liver model, which based upon abdominal CT data ofhuman, is more practical than the simple model. The simulation oftemperature-controlled mode, which used the proportional-integral controlled algorithmwith the feedback temperature, can not only operate and being referred to easily, butalso prevent tissue coagulation from overheating effectively. These results indicate thatthe temperature-controlled mode has certain superiority in regulating the RF power, thusprovides certain references for personalized treatment planning of RFA.