A Simulation of Gas-Based, Endometrial-Ablation Therapy

The comparison of lesion outline and temperature field determined by different ways in atrial radiofrequency ablation

BACKGROUND

The aim of this study is to research the lesion outline and temperature field in different ways in atrial radiofrequency ablation by using finite element method.

METHODS

This study used the method which considered the thermal dosage to determine the boundary between viable and dead tissue, and compared to the 50 °C isotherm results in analyzing lesion outline. Besides, we used Hyperbolic equation which considered the relaxation time to calculate the temperature field and contrasted it with Pennes' bioheat transfer equation.

RESULTS

As the result of the comparison of the lesion outline, when the ablation time was 120 s, the isotherm of the thermal dosage was larger than the 50 °C isotherm and with the increasing of the voltage the gap increased. When the ablation voltage was 30 V, the 50 °C isotherm was larger than the thermal dosage isotherm when the ablation time was less than 160 s. The isotherms overlapped when the time was 160 s. And when the ablation time was more than 160 s, the 50 °C isotherm was less than the thermal dosage isotherm. As to the temperature field, when the ablation voltage was 30 V with the ablation time 120 s the highest temperature decided by Hyperbolic was 0.761 °C higher. The highest temperature changed with relaxation time. In most cases, the highest temperature of the Hyperbolic was higher otherwise the relaxation time was 30-40 s.

CONCLUSIONS

It is better to use CEM43 °C to estimate the lesion outline when the ablative time within 160 s. For temperature distribution, the Hyperbolic reflects the influence of heat transmission speed, so the result is more close to the actual situation.

Numerical and ex vivo studies of a bioprobe developed for laser-induced thermotherapy (LITT) in contact with liver tissue

This work is based on the production of a bioprobe that is compatible with magnetic resonance imaging (MRI) for laser-induced thermotherapy (LITT) in liver cancer laser therapy. This probe is made of an alumina tube (3-mm diameter) in which an optical fibre is centred and fixed. A shooting window (20mm) is created using a mechanical rectifier. The device is then consolidated by the injection of a transparent and heat-resistant resin. Through numerical modelling, the thermal power damping of the laser source is evaluated as well as the propagation of the heat in the ex vivo liver tissue according to different heating scenarios. These analyses allow for an estimation of the irradiated volume. Ex vivo tests were performed on bovine liver to confirm the adequacy of the bioprobe for LITT and of the irradiated volumes predicted by the numerical model. There was a difference of 8% between the simulations and ex vivo experiments. The pulsed mode heating scenario was the most effective under the experimental conditions.

Validation of Numerically Simulated Tissue Temperatures During Transcutaneous Recharge of Neurostimulation Systems

OBJECTIVE

A research study combining numerical simulation and animal-model experiments has been performed to assess the ability of simulation to accurately calculate temperatures within living tissue during the recharge of a neuromodulation system (Restore Ultra device, Medtronic Neuromodulation, Minneapolis, MN, USA).

MATERIALS AND METHODS

The experiments were carried out on a sheep with the neuromodulation implant set to depths of 0.6 cm and 2.1 cm. Temperatures were recorded on the surfaces of the implant and on the sheep skin. Finite element simulations were carried out to determine the degree to which the simulations and experiments match. Additional calculations were performed for an intermediate implant depth.

RESULTS

It was found that there was excellent agreement between the simulations and the animal model for both depths.

CONCLUSION

It is shown that numerical simulation using the Pennes bioheat equation is capable of predicting temperature increases within living tissues when implanted heat-generating devices are in use. The device used in the present study does not give rise to temperatures which cause concern of thermal injury or safety. The study was performed for aligned antenna and implant.

Theoretical Modeling for Hepatic Microwave Ablation

Thermal tissue ablation is an interventional procedure increasingly being used for treatment of diverse medical conditions. Microwave ablation is emerging as an attractive modality for thermal therapy of large soft tissue targets in short periods of time, making it particularly suitable for ablation of hepatic and other tumors. Theoretical models of the ablation process are a powerful tool for predicting the temperature profile in tissue and resultant tissue damage created by ablation devices. These models play an important role in the design and optimization of devices for microwave tissue ablation. Furthermore, they are a useful tool for exploring and planning treatment delivery strategies. This review describes the status of theoretical models developed for microwave tissue ablation. It also reviews current challenges, research trends and progress towards development of accurate models for high temperature microwave tissue ablation.

Theoretical modeling for hepatic microwave ablation

Thermal tissue ablation is an interventional procedure increasingly being used for treatment of diverse medical conditions. Microwave ablation is emerging as an attractive modality for thermal therapy of large soft tissue targets in short periods of time, making it particularly suitable for ablation of hepatic and other tumors. Theoretical models of the ablation process are a powerful tool for predicting the temperature profile in tissue and resultant tissue damage created by ablation devices. These models play an important role in the design and optimization of devices for microwave tissue ablation. Furthermore, they are a useful tool for exploring and planning treatment delivery strategies. This review describes the status of theoretical models developed for microwave tissue ablation. It also reviews current challenges, research trends and progress towards development of accurate models for high temperature microwave tissue ablation.