RF ablation at low frequencies for targeted tumor heating: in vitro and computational modeling results.

RF ablation uses RF current to heat and kill cancer applied via an electrode inserted under image guidance. Tumor has about half the electrical resistivity of normal tissue below 20 kHz, but similar resistivity above 500 kHz. We placed normal porcine liver tissue in contact with agar gel having similar resistivity as tumor within 20-450 kHz.

Sequential activation of ground pads reduces skin heating during radiofrequency ablation: initial in vivo porcine results.

Purpose: Radiofrequency (RF) ablation is a common treatment modality for inoperable liver cancer. Skin burns below ground pads during RF ablations are increasingly prevalent, hindering the development of higher-power RF generators capable of creating larger ablation zones.

Materials And Methods: 9 RF ablations (n=4 simultaneous, n=5 sequential) were performed with 300 W for 12 min via two internally cooled cluster electrodes placed in the gluteus maximus of domestic swine.

Sequential activation of ground pads reduces skin heating during radiofrequency tumor ablation: in vivo porcine results.

Skin burns below ground pads during monopolar RF ablation are increasingly prevalent, thereby hindering the development of higher power RF generators capable of creating larger tumor ablation zones in combination with multiple or new applicators. Our goal was to evaluate reduction in skin temperatures via additional ground pads in an in vivo porcine model. Three ground pads placed on the animal's abdomen were activated either simultaneously or sequentially, where activation timing was adjusted to equilibrate skin temperature below each pad.

Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation.

We measured the ex vivo electrical conductivity of eight human metastatic liver tumours and six normal liver tissue samples from six patients using the four electrode method over the frequency range 10 Hz to 1 MHz. In addition, in a single patient we measured the electrical conductivity before and after the thermal ablation of normal and tumour tissue. The average conductivity of tumour tissue was significantly higher than normal tissue over the entire frequency range (from 4.

Tumor ablation at low frequencies for preferential tumor heating: initial ex-vivo tissue studies.

Purpose: Radiofrequency (RF) ablation is a common treatment modality for inoperable liver cancer. Several studies have demonstrated that significant differences exist between the electrical properties of tumor and normal tissue, especially at lower frequencies. In this study, we investigated in an ex vivo setting whether the use of lower frequencies during ablation results in preferential heating of tumor tissue.

Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation.

Purpose: Finite element method (FEM) models are commonly used to simulate radio frequency (RF) tumor ablation. Prior FEM models of RF ablation have either ignored the temperature dependent effect of microvascular perfusion, or implemented the effect using simplified algorithms to reduce computational complexity. In this FEM modeling study, the authors compared the effect of different microvascular perfusion algorithms on ablation zone dimensions with two commercial RF electrodes in hepatic tissue.

Sequential activation of a segmented ground pad reduces skin heating during radiofrequency tumor ablation: optimization via computational models.

Radiofrequency (RF) ablation has become an accepted treatment modality for unresectable tumors. The need for larger ablation zones has resulted in increased RF generator power. Skin burns due to ground pad heating are increasingly limiting further increases in generator power, and thus, ablation zone size.

Sequential activation of multiple grounding pads reduces skin heating during radiofrequency tumor ablation.

Purpose: Radiofrequency (RF) tumor ablation has become an accepted treatment modality for tumors not amenable to surgery. Skin burns due to ground pad heating may become a limiting factor for further increase in ablation zone dimensions and generator power. We investigated a method were groups of ground pads are sequentially activated to reduce skin heating.

In vitro measurements of temperature-dependent specific heat of liver tissue.

We measured the specific heat of liver tissue in vitro by uniformly heating liver samples between two electrodes. We insulated the samples by expanded polystyrene, and corrected for heat loss and water loss. The specific heat of the liver is temperature-dependent, and increases by 17% at 83.

Measurement of temperature-dependent specific heat of biological tissues.

We measured specific heat directly by heating a sample uniformly between two electrodes by an electric generator. We minimized heat loss by styrofoam insulation. We measured temperature from multiple thermocouples at temperatures from 25 degrees C to 80 degrees C while heating the sample, and corrected for heat loss.

Large-volume radiofrequency ablation of ex vivo bovine liver with multiple cooled cluster electrodes.

Three methods of creating large thermal lesions with cool-tip cluster electrodes were compared. Three cluster electrodes were arranged 4 cm apart in a triangular array. Eight lesions were created ex vivo in fresh bovine liver (from a butcher) with each method: sequential ablation (three electrodes, 12 minutes each); simultaneous activation of electrodes (12 minutes); and rapid switching of power between electrodes (12 minutes), for which an electronic computer-controlled switch was developed.