Irreversible electroporation of the porcine kidney: Temperature development and distribution.

OBJECTIVE: Although tissue ablation by irreversible electroporation (IRE) has been characterized as nonthermal, the application of frequent repetitive high-intensity electric pulses has the potential of substantially heating the targeted tissue and causing thermal damage. This study evaluates the risk of possible thermal damage by measuring temperature development and distribution during IRE of porcine kidney tissue.
METHODS: The animal procedures were conducted following an approved Institutional Animal Ethics Committee protocol. IRE ablation was performed in 8 porcine kidneys. Of them, 4 kidneys were treated with a 3-needle configuration and the remaining 4 with a 4-needle configuration. All IRE ablations consisted of 70 pulses with a length 90 µs. The pulse frequency was set at 90 pulses/min, and the pulse intensity at 1,500 V/cm with a spacing of 15 mm between the needles. The temperature was measured internally using 4 fiber-optic temperature probes and at the surface using a thermal camera.
RESULTS: For the 3-needle configuration, a peak temperature of 57°C (mean = 49 ± 10°C, n = 3) was measured in the core of the ablation zone and 40°C (mean = 36 ± 3°C, n = 3) at 1cm outside of the ablation zone, from a baseline temperature of 33 ± 1°C. For the 4-needle configuration, a peak temperature of 79°C (mean = 62 ± 16°C, n = 3) was measured in the core of the ablation zone and 42°C (mean = 39 ± 3°C, n = 3) at 1cm outside of the ablation zone, from a baseline of 35 ± 1°C. The thermal camera recorded the peak surface temperatures in the center of the ablation zone, reaching 31°C and 35°C for the 3- and 4-needle configuration IRE (baseline 22°C).
CONCLUSIONS: The application of repetitive high-intensity electric pulses during IRE ablation in porcine kidney causes a lethal rise in temperature within the ablation zone. Temperature monitoring should be considered when performing IRE ablation near vital structures.