Metodologie di analisi elettromagnetica e termica per procedure di termoablazione RF

This dissertation has two aims: 1. the development of an equivalent electromagnetic model to predict the spatial distribution of the induced current, of the power losses and of the temperature inside the human body during a radio frequency (RF) thermo-ablation procedure (applied to kidney and liver) and 2. the development of conceptual tools useful to the operators to allow a better and optimized use of the thermo-ablation system during the surgeries. The first aim is reached through two phases. The first one is the identification of the better numerical technique for the analysis of electromagnetic fields inside biological tissues. This technique has been identified in the Finite Integration Technique (FIT) supported and integrated by the Perfect Boundary Approximation (PBA) technique. They are fully implemented into the CST Studio Suite 2011 and in particular into the Microwave Studio tool that has been used through this work. The second one is the development of a virtual human model compatible with the FIT algorithm. Based on the studies carried out inside the Visible Human Project an equivalent human model has been developed called "UAq Ales" (University of L'Aquila Anatomical Library for Electromagnetic Simulations) or simply "Ales" used for all simulations presented in this work. The thermal analysis has been extended by using a suitably developed macro (on VBA), considering the steady-state solution of the bioheat equation governing the heat exchange among biological tissues. The models developed have been validated by comparing the numerical results to those obtained by experimentally applying the RF thermo-ablation procedure to ex vivo and in vivo cases so obtaining a reasonable agreement among computed and measured results. The second aim is reached by the extraction, from the computed and measured data, of graphs linking the main variables needed for the correct development of the thermal-ablation procedure. They give the operators a preliminary indication on the setting of the variables and the strategies to be adopted in the functioning of the system. This dissertation gathers the electromagnetic modelling activities and the experimental ones carried out in the last three years inside the collaboration frame between the UAq EMC Laboratory of the University of L'Aquila and the medical team of Prof. Dott. Bruno Zobel of the Policlinico Universitario del Campus Bio-Medico in Rome. This work is aimed to determine a methodology able to predict the effects (in terms of temperature and extension of the lesion ) of the electromagnetic energy transferred from the RF electrodes to the necrotic tissues in a way to better address the operations of the use of the electromedical systems used for this kind of procedures.