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The pancreas is adjacent to critical organs; excessive microwave ablation (MWA) can result in serious complications. The purpose of this paper is to provide the reference data of pancreas MWA for clinicians, analyze the ablation outcomes under different ablation parameters, and determine the critical temperature of pancreatic surface fat liquefaction outflow. Combinations of two power levels (30 W and 55 W), three antenna diameters (1.3 mm, 1.6 mm, and 1.9 mm), and three ablation times (1 min, 1.5 min, and 2 min) were applied to an ex vivo pig pancreas. Temperature measurements were taken at four thermocouple points. The center point is located 5 mm horizontally from the antenna slot, with a temperature measurement point located 5 mm above, below, and to the right of the center point. Main effect analysis and variance analysis were used to quantify the influences of each factor on the ablation outcomes. At 30 W, the antenna diameter contributing the most at 48.5%. At 30 W–1.3 mm–1 min, the spherical index (1.41) is closest to 1. At 55 W, the coagulation zone size was almost only affected by the ablation time, with a contribution rate of 28.7%, the temperature at point C exceeds point B. On the surface of the ex vivo porcine pancreas, the fat outflow temperature was 54ã. Ablation combinations with low power, short duration, and small antenna diameter results in a more nearly spherical coagulation zone. When performing MWA on the pancreas, it is advisable to avoid areas with higher fat content, while keeping the pancreatic surface temperature below 54°C. [ABSTRACT FROM AUTHOR]

Lung tumor is the first malignant tumor with the highest mortality, but only no more than one-third of patients can be treated by surgical resection. Microwave ablation (MWA) has become a new adjuvant therapeutic mean for lung tumors because of its low trauma, short treatment time, large ablation volume and wide application range. However, the treatment parameters of MWA, such as input power and ablation time, still depend on the doctors' experience, which leads to the ineffectiveness of MWA. Therefore, the accurate modeling of temperature distribution of lung tumor MWA has become a significant technical problem to be solved. Recent research was devoted to personalized characterization of lung tumor parameters, finite element analysis of temperature distribution in MWA and accurate ablation effect evaluation. In this paper, a review of the recently obtained results and data will be presented and discussed. [ABSTRACT FROM AUTHOR]

Purpose: To propose an improved specific absorption rate (SAR) computation method by incorporating a thermal conductivity item, develop mathematical simulation models based on the SAR, and enhance the accuracy of temperature simulation for 2450-MHz microwave fields.Materials and methods: Experimental data of 2450-MHz microwave antenna were obtained with a phantom and then new SAR equations were calculated according to Pennes bio-heat transfer equation. Next, the SAR equations were regarded as heating sources and SAR-derived temperature changes were simulated numerically; Finally, temperature measurement results were compared with simulation data to validate the accuracy of the new SAR method.Results: The simulated and measured temperature changes were generally in good agreement for the phantom. According to comparison results, the maximum error was less than 6 °C, the average error was less than 2 °C, and the standard deviation was less than 1 °C.Conclusions: This new SAR-derived simulation method can significantly simplify the simulation process and improve the prediction accuracy of microwave ablation temperature field. [ABSTRACT FROM PUBLISHER]

The temperature distribution in the region near a microwave antenna is a critical factor that affects the entire temperature field during microwave ablation of tissue. It is challenging to predict this distribution precisely, because the temperature in the near-antenna region varies greatly. The effects of water vaporisation and subsequent tissue carbonisation in an ex vivo porcine liver were therefore studied experimentally and in simulations. The enthalpy and high-temperature specific absorption rate (SAR) of liver tissues were calculated and incorporated into the simulation process. The accuracy of predictions for near-field temperatures in our simulations has reached the level where the average maximum error is less than 5°C. In addition, a modified thermal model that accounts for water vaporisation and the change in the SAR distribution pattern is proposed and validated with experiment. The results from this study may be useful in the clinical practice of microwave ablation and can be applied to predict the temperature field in surgical planning. [ABSTRACT FROM AUTHOR]

It is critical for microwave ablation (MWA) treatment planning to evaluate the changes of thermal coagulation zones. In MWA procedures, the shapes and sizes of thermal coagulation zones are gradually evolving over time. To this end, a novel characterization and mapping method of thermal coagulation zones is presented in this article. Firstly, finite element method (FEM) models of temperature distributions for 40, 45, 50, 55, and 60 W microwave ablations were built to derive thermal ablation data of ex vivo porcine livers and were compared with experimental results. Secondly, growth models of characteristic lengths were fitted. Finally, characterization functions of thermal coagulation zones were developed using these growth models. In addition, shape variation factors were incorporated to handle the minor shape variations of thermal coagulation zones. Experimental results showed that these characterization functions could accurately represent the changes of thermal coagulation zones. The standard deviations between prediction results and simulated values were less than 1 mm. The comparative results were statistically analyzed by paired t test (P > 0.05), indicating no significant differences. The proposed method can simply and effectively predict the changes of MWA coagulation zones with time, thus providing reliable coagulation dimensions for the thermal ablation therapies. [ABSTRACT FROM AUTHOR]

Temperature predictions of microwave ablation (MWA) are currently restricted by the specific temperature‐dependent data of tissue characteristic parameters. To address this issue, a new parameter feedback method based on temperature simulations and single‐thermometry measurements was presented. Experimental data of 2450‐MHz microwave antenna was obtained from ex vivo porcine livers. A temperature distribution model was constructed, and the contributions of characteristic parameters were acquired by the sensitivity analysis method. Subsequently, parameter feedbacks were conducted based on a minimization of the errors between numerical data and single‐thermometry measurements. The temperature distribution model was then optimized using the feedback parameters. Finally, temperature measurements were compared with simulation data to validate the accuracy of the model. According to the temperature distribution model with parameter feedback, the averages of maximum error, average error, as well as SD between the simulation temperatures and the measurements were 2.952, 1.323, and 0.852°C, respectively. The simulated and measured temperature changes were generally in good agreement. The proposed method can be useful in MWA temperature simulations to improve temperature prediction accuracy. [ABSTRACT FROM AUTHOR]