ETherm3 is a finite-element software suite for simulations of electrosurgery and RF thermal ablation processes. Program components cover the complete calculation process from mesh generation to solution analysis. The solutions employ three-dimensional conformal meshes to handle cluster probes and other asymmetric assemblies. The conformal-mesh approach is essential for high-accuracy surface integrals of net electrode currents. ETherm3 performs coupled calculations of RF electric fields in conductive dielectrics and thermal transport via dynamic solutions of the bioheat equation. The boundary-value RF field solution is updated periodically to reflect changes in material properties. ETherm3 features advanced material models with the option for arbitrary temperature variations of thermal and electrical conductivity, perfusion rate, and other quantities. The code handles irreversible changes by switching the material reference of individual elements at specified transition temperatures. ETherm3 is controlled through a versatile interpreter language to enable complex run sequences. The code can automatically maintain constant current or power, switch to different states in response to temperature or impedance information, and adjust parameters on the basis of user-supplied control functions. In this paper, we discuss the physical basis and novel features of the code suite and review application examples.
Ablation of the endometrium has become a viable treatment for dysfunctional bleeding of the uterus in women. Surgical applications of thermal ablation utilized a rolling electrode to ablate the inner uterine lining, but required practiced surgical skills and made it difficult to assess subsurface damage. Recently, various energy systems have been applied to the endometrium such as lasers, microwaves, RF electrodes, hot water balloons, and cryotherapy. A finite element model is presented to compare a multi-electrode, multiplexed RF device with a balloon containing hot fluid. The temperature fields in the uterine wall are plotted over time for various blood flow values. Assumptions of constant electrical conductivity are compared to temperature- dependent electrical conductivity. Temperatures are shown to be a maximum of about 10 - 20 degree(s)C higher when varying electrical conductivity is used. Results are also shown for cases with a 2 mm blood vessel in the field and how each device adjusts its operation to compensate for this heat sink. Damage integral results will be shown according to the time and temperature of the treatments.
1407_57The SBS_1 experiment at Sandia National Laboratories is designed to demonstrate the feasibility of the Scanning Beam Switch for high-power rf generation. The primary application is to pulsed rf linacs and high-frequency induction accelerators. It is expected that the apparatus will generate rf output power exceeding 100 MW at 50 MHz over a 5 microsecond(s) pulse. The device can operate as an oscillator or high gain amplifier. To achieve the capability for long-macropulse and high-duty-cycle operation, SBS_1 uses a large dispenser cathode and vacuum triode input driver.