Experimental validation of MWA effects on biological tissue by sensorized needles based on FBG technology

The aim of the present study was to simulate and experimental assess the temperature distribution and damaged tissue in ex vivo porcine livers undergoing microwave ablation (MWA). Firstly, the interaction between microwave (MW) and liver was simulated to predict tissue temperature distribution and damaged volume; then numerical simulations were experimentally validated. Simulations were performed: i) by considering the geometry of the MW antenna used during the experiments, ii) by implementing the Pennes' equation to calculate the temperature map within the tissue, and iii) by using Arrhenius model to calculate the damaged tissue. The model was validated by performing experiments on four ex vivo pig livers, which were treated using a 2.45 GHz antenna at 100 W for 4 min. Three custom probes were fabricated and calibrated to measure tissue temperature during MWA. These probes consist of a needle embedding one or more Fiber Bragg grating (FBG) sensors. The three probes embed a total of eight FBGs, hence tissue temperature during MWA was monitored at eight distances from the antenna. Simulated temperatures around the antenna agree with experimental data. Moreover, the predicted damaged volume agrees with the volume of coagulation experienced by the tissue undergoing MWA. In conclusion, the proposed thermometric probes allow performing distributed temperature measurement during MWA, as well as facilitate the insertion of the FBGs within the organ. The measurements show that the model is able to accurately predict MWA effects in an ex vivo pig liver.