Overcoming the limitations of radiofrequency ablation in treating early-stage hepatocellular carcinomas

Abstract

Radiofrequency ablation (RFA) is a local and minimally invasive thermal therapy, used in the treatment of the hepatocellular carcinomas (HCCs) for last 30 years. Though the field of RFA has remained progressive since its conception, still there’s no single solution for the problems of – (1) Heat sink effect, (2) Thermal injury to neighbouring organs and, (3) Sacrifice of normal functioning tissue. The root cause of these problems is the absence of functionality in in-practise RFA technology to offer bias in the spatial distribution of the current density. Specifically, in-practise RFA technology only offers an axis-symmetric current density distribution, which incurs a corresponding axis-symmetric thermal damage zone. The dissertation work includes study on an electrode, which could be a single solution for the problems of the heat sink effect, injury to neighbouring organs and sacrifice of normal tissue. A numerical study on the feasibility of this electrode to achieve biased current density and hence biased ablation (often called directional ablation herein) has been performed. Further, a new method has been proposed to perform a systematic study in a feasible time to explore different asymmetrical ablation shapes achievable with this electrode. With the help of this method, a pre-simulated database has been created. In conjunction with our in-house algorithm, this database has been shown to avoid sacrificing normal tissue during RFA of irregularly shaped segmented HCC tumours. This dissertation also includes preliminary work on the heat sink effect and injury to extrahepatic organs during RFA. Herein, an experimental approach with minimal approximations and realistic information has been used to calculate convective heat transfer coefficient. This would help in suggesting the correct amount of bias required in the input power to overcome heat sink effect. Computer modelling of RFA using actual anatomical structures extracted from the CT images has been performed to overcome thermal injury to the neighbouring organs. This study highlights the most significant parameters that influence injury to neighbouring organs. These parameters and the relative positioning of the tumour from the extrahepatic organs would help in assisting necessary bias in the ablation during the pre-planning stage of therapy. Finally, this dissertation finishes by touching upon prospects.