How do I design an RF ablation probe for minimally invasive surgical applications?

Designing an RF ablation probe for minimally invasive surgery requires a needle-like electrode (typically 14-17 gauge, 1.6-2.1 mm diameter, 10-25 cm length) connected to an RF generator operating at 375-500 kHz that delivers 50-200 watts of RF current through the tissue to create a controlled spherical zone of coagulation necrosis (cell death) around the electrode tip. The probe design must address: electrode geometry (exposed tip length of 1-4 cm determines the initial heating zone; multi-tine deployable electrodes expand from a single needle to create larger ablation volumes of 3-7 cm diameter); impedance monitoring (tissue impedance starts at 50-150 ohms and rises sharply as coagulation occurs and water boils, indicating treatment progress); temperature monitoring (thermocouples embedded in the electrode tip measure tissue temperature, targeting 60-100 degrees C for complete cell death while avoiding excessive charring above 110 degrees C that increases impedance and limits ablation size); and internally cooled electrodes (circulating chilled saline through the electrode shaft prevents charring at the electrode surface, allowing higher power delivery and larger ablation zones). The RF generator uses monopolar configuration with a large dispersive ground pad on the patient's skin to complete the current circuit.