Numerical and experimental characterization of radiofrequency ablation in perfused kidneys

Abstract

We develop a three-dimensional finite element model in order to predict the resulting temperature distribution of a radiofrequency ablation (RFA) treatment in human kidneys. Here, a strong cooling effect results from a high degree of blood perfusion, which is modeled via two different approaches. The influence of big blood vessels for treatments close to renal hilus is modeled by including a cylindrical cooling tube based on the renal artery (or vein) in the kidney model. The influence of the perfusion of small arterioles and capillaries is represented by Pennes' approach in the bioheat equation. The experimental validation is performed by an in vivo RFA treatment on porcine kidney. Prior to the in vivo measurements several ex vivo experiments on fresh kidneys are carried out as a plausibility check for the model. During the treatments temperature profiles are measured using thermocouples which are radially arranged around the RFA applicator trocar. The evaluated data for each sensor show a deviation between 0.01 and 12 % from the simulation results. The approach serves for the design of a preplanning tool for RFA treatment in the future.

Archives of Electrical Engineering

“…Next, the thermal damage of hepatic tissue for the multi-tine applicator and pre-defined limit values of electrode voltage was specified based on the Arrhenius model. Similar considerations can be found in several related papers concerning different kind of electric probes [16][17][18][19][20][21][22][23][24][25][26][27].…”

“…Moreover, σ (S/m) means the electric conductivity of a given medium and φ (V) is the electric potential. Such an assumption is true for the RF range of 450-550 kHz, where the wavelength of the EM excitation (λ = c 0 / f ≈ 600 m) is much larger than the dimensions of the analyzed geometry (about 10 000 times more than the largest applicator size, see Table 1) [16]. Therefore, the displacement currents are negligibly compared to the conduction currents [12].…”

“…For simplicity, the presented 3D model of RF heating of liver tissue assumes a quasi-static approximation for an electro-conductive field based on the following equations [16]:…”

“…Importantly, the blood parameters are provided with subscript 'b', as in the case of ω b (1/s), which means the blood perfusion rate in liver tissue. Moreover, the term Q ext (W/m 3 ) denotes the Joule heating [12,16,18,26]:…”

The Feasibility of Mathematical Modeling for Hemostatic Sutures Comparison in a Partial Nephrectomy

“…Одним из перспективных направлений является применение математического моделирования для описания процессов, происходящих в органах при нормальном и патологическом функционировании, во время и после оперативных вмешательств. В частности, математическое методы применяются для моделирования патологических процессов в почках и их хирургической коррекции, таких как моделирование зоны коагуляционного некроза при применении микроволновой и криохиругии; моделирование процессов повреждения почек при их травме; изучение влияния дистанционной литотрипсии на паренхиму почки; прогнозирование прогрессии опухолевой ткани в почке; усовершенствование лучевых методов диагностики заболеваний почек [7,8,9,10,11,12,13,14]. Работы, описывающие математические модели паренхимы почки с наложенными гемостатическими швами, в доступной нам литературе отсутствуют.…”