Parameters optimization of bipolar high frequency pulses on tissue ablation and inhibiting muscle contraction

Irreversible electroporation (IRE) is an emerging technology for the non-thermal ablation of tumors, but it is challenged due to the unintended induction of muscle contractions, which must be avoided by neuromuscular blockade in clinic. In this study, high frequency irreversible electroporation (H-FIRE), which replaces the monopolar IRE pulses with a burst of bipolar pulses, was used for tissues ablation on rabbit liver through Plate Electrodes. The bursts with different individual pulse durations maintain a constant total energized time (100 μs), burst number (90), and inter-burst delay (1 s). An accelerometer was used to measure the muscle contraction intensity. After the experiments, the tissue sections were made for pathological analysis. The experimental results show that all the cells are intact in the treated tissues that were harvested immediately. The tissues, which were harvested three days after the experiments, have an obvious ablation area, and the necrosis degree is increased with the pulse voltage and individual pulse width of the bursts. The extent of muscle contractions caused by H-FIRE is less than IRE. In addition, the simulations of electric field distribution near the vessels in liver tissues show that with the increase of the frequency and decrease of the pulse duration of the bursts, the electric field distribution will be more uniform. Compared with the lethal thresholds, bursts with larger pulse width can ablate the liver tissues effectively. Integrating into account the ablation effect and muscle contraction, we consider that H-FIRE with the individual pulse durations for 5 μs, electric field intensity for 2000 V/cm, can replace the traditional IRE, which have a good ablation effects and less extent of muscle contractions for animals.