A Simulation of Gas-Based, Endometrial-Ablation Therapy

Abstract

The method of numerical simulation has been employed to evaluate the use of a gas as a heating medium for endometrial ablation for the treatment of menorrhagia and uterine fibroids. The simulations encompassed fluid flow and heat transfer within the gaseous medium which serves to heat the uterine lining and the coupled heat conduction in the uterine tissue. For the case study featured here, helium at a temperature of 140 degrees C was employed as the heating medium. A total therapy duration of 6 min was modeled. The outcome of the simulation has provided quantitative information about the detailed necrosis depths that can be attained by the application of the therapy. In particular, necrosis depths on the order of 5 mm were achieved. It was also shown that by making use of a tailored pattern of fluid flow within the uterine cavity, particular zones on the uterine lining such as fibroids can be selectively targeted. Furthermore, the duration of the therapy needed to achieve a desired degree of necrosis can be predicted in advance. The advantages of a gas-based therapy relative to a liquid-based therapy are identified. Significant among these is the capability of the gas-based therapy to target specific zones which require treatment, while sparing healthy tissue. Another significant advantage of gas-based therapy is that it enables the use of higher temperatures which, in turn, allows the therapeutic process to be performed in a shorter time duration.

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

“…In the first situation the temperature distribution in the cardiac model was obtained by solving the Pennes’ bioheat transfer equation [12, 26–28]. where is tissue density (kg/m 3 ), c is specific heat of tissue (J/kg °C), k is the thermal conductivity (W/m °C), T is the temperature, Qr is the heat source(W/m 3 ), and Q m is the perfusion heat loss.…”

Theoretical Modeling for Hepatic Microwave Ablation~!2009-10-21~!2009-12-30~!2010-02-04~!

“…The comprehensive computer model provided good correlation with experimentally measured temperatures Fig. ( 2 ) shows an image of the ablation zone created in ex vivo bovine tissue, compared to simulated temperature profiles, taken from [45]. …”

“…Nevertheless, these models are an improvement over simple SAR models since they account for thermal conduction and blood perfusion, in the case of in vivo studies. Moreover, although tissue temperatures in the target region may be large, the extent of ablation zones measured using these models correlates well with ablation zones created in ex vivo experiments [45]. …”

“…Since tissue physical properties do not change for this model, there is no need to recompute Q during the course of the ablation—that is, the coupling between the electromagnetic and thermal models is only in one direction. While such a model is relatively easy to implement, tissue temperatures obtained from such models are unrealistically large since they do not account for reduced tissue conductivity and permittivity at higher temperatures, as well as the significant heat sink associated with water vaporization [45]. Nevertheless, these models are an improvement over simple SAR models since they account for thermal conduction and blood perfusion, in the case of in vivo studies.…”

“…Yang et al [45, 73] presented a comprehensive computer model of high power microwave tissue ablation, incorporating dynamic changes in tissue dielectric and thermal properties, based on experimental measurements of tissue water content [39]. Their studies presented a mapping function to compute tissue water content from temperature.…”