Optimization of an Endoscopic Radiofrequency Ablation Electrode

Radiofrequency ablation (RFA) is an increasingly used, minimally invasive, cancer treatment modality for patients who are unwilling or unable to undergo a major resective surgery. There is a need for RFA electrodes that generate thermal ablation zones that closely match the geometry of typical tumors, especially for endoscopic ultrasound-guided (EUS) RFA. In this paper, the procedure for optimization of an RFA electrode is presented. First, a novel compliant electrode design is proposed. Next, a thermal ablation model is developed to predict the ablation zone produced by an RFA electrode in biological tissue. Then, a multi-objective genetic algorithm is used to optimize two cases of the electrode geometry to match the region of destructed tissue to a spherical tumor of a specified diameter. This optimization procedure is then applied to EUS-RFA ablation of pancreatic tissue. For a target 2.5 cm spherical tumor, the optimal design parameters of the compliant electrode design are found for two cases. Cases 1 and 2 optimal solutions filled 70.9% and 87.0% of the target volume as compared to only 25.1% for a standard straight electrode. The results of the optimization demonstrate how computational models combined with optimization can be used for systematic design of ablation electrodes. The optimization procedure may be applied to RFA of various tissue types for systematic design of electrodes for a specific target shape.

Optimization of a Compliant Endoscopic Radiofrequency Ablation Electrode

Radiofrequency ablation (RFA) is a common cancer treatment modality for patients who are ineligible for open surgery. There is a need for RFA electrodes that generate heating zones that closely match the geometry of typical tumors, especially for endoscopic ultrasound-guided (EUS) RFA. In this paper, the procedure for optimization of an RFA electrode is presented. First, a novel compliant electrode design is proposed. Next, a thermal ablation model is developed to predict the ablation zone surrounding an RFA electrode in biological tissue. Then, a multi-objective genetic algorithm is used to optimize two cases of the electrode geometry to match the region of destructed tissue to a spherical tumor of specified diameter. This optimization procedure is applied to an EUS-RFA ablation of pancreatic tissue. For a target 2.5cm spherical tumor, the optimal design parameters of the compliant electrode design were found. After simulating 40 generations of 50 designs per generation, both cases converged to optimal solutions. The objective functions were useful for simple electrode designs. For more complex electrode designs, the objective functions were unable to direct the design toward a 2.5cm sphere. The results of the optimization demonstrate how computational models combined with optimization can be used for systematic design of ablation electrodes. The optimization procedure may be applied to RFA of various tissue types for systematic design of electrodes that generate spherical ablation zones.

Wind Power Micro-Generator Using Dielectric Electric Active Polymer

Wind power is emerging as a particularly attractive form of renewable energy. Dielectric Electric Active Polymers (DEAP) has shown great potential as actuator materials. Their predomination has been shown to operate in transforming mechani­cal to electrical energy in a generator mode. This work investigates the principle of wind power dielectric electro active polymer generator, simulation and experimental verification of the phenomenon. Dielectric Electro Active Polymer have proved to provide electrical energy with density as high as 1.5J.g-1.This value is very important compared to the density available with piezoelectric polymer (0.3J.g-1). The prototype has been set up on the DEAP wind power generator in the article. It is a membrane with an area of 1.5 m2 and 30μm in thickness, which is fabricated by Danfoss PolyPower A/S using smart compliant electrode technology in conjunction with a silicone elastomer. In the last part of this article, experimental results are detailed with our prototype for wind application.