Suitable Use of Nanostructures in the Treatment of Tumors by the Radiofrequency Ablation Method

Abstract

Radiofrequency ablation (RFA) is a minimally invasive method, suitable for treatment of irresectable primary and secondary tumors. The principle of this method is to supply electric current to the target’s centre where it causes coagulative necrosis. Electric current, generated by a radiofrequency (rf.) generator, is used for ablation. Electrodes of different shape and dimensions (according to the type of tumor tissue and lesion shape and size) are then used to optimize 3D distribution of electric current in the area to be treated. If tumor centers are of approximately spherical shape, that could be generated by the use of electrodes, then the treatment will be effective. More irregular the tumor shape is, faster the treatment effect decreases. High doses of energy are concentrated in the immediate vicinity of the applicator resulting in heat production. Considerable heat loss occurs as the transfer of thermal energy decreases rapidly with distance. Moreover, the thermal energy transfer is significantly influenced by the thermal conductivity, therefore, it depends on the conductivity parameters (including perfusion) of tissues. Thus, the resultant thermal effect may be insufficient to completely treat the predicted tumor area. Other treatment limitations are the total treatment volume and therapeutic time both limited by the maximal temperature near the end of the applicator; temperature above 105°C leads to tissue carbonization and the loss of current conduction in the treated tissue. To improve the effects of treatment methods, there are different solutions: by reducing or increasing the power source of radiofrequency energy, by influencing the spread of current or by influencing the tissue response. Application of suitable combination of nano-particles (because of their dimensions and unique physical and chemical properties) represents a new approach to improve the effects of treatment methods; the applied nano-particles induce selective thermal energy spreading beyond the effective applicator range. It represents an application of nano-biotechnology in this type of medical treatment. The aim of this study is to demonstrate the efficacy of topical application of suitable nanoparticles directly into the tumor before using the applicator for local heating of tissue. This paper will demonstrate that the use of nano-particles (iron oxide) in the method of radiofrequency ablation will influence the size and progress of the final ablation lesion. Experiments were performed on samples of the liver and kidney of pigs and ex vivo on prepared agar phantoms of special materials simulating homogeneous tissue with the application of nanoparticles directly into the tissue (phantom) in the established RF applicator. The source of radiofrequency energy was RITA generator with an operating frequency of 460 kHz, power of 90W. The present work demonstrates that the prepared and applied nanomaterials iron oxide (prepared by the method of Tada et al and Qu et al) can lead to an increase in the resulting ablation spheres up to 50% and shortening the time required to achieve the resulting sphere. It will be proved by the experiment presented in this article.