Solazzo Stephanie A, Liu Zhengjun, Lobo S Melvyn, Ahmed Muneeb, Hines-Peralta Andrew U, Lenkinski Robert E, Goldberg S Nahum
Minimally-Invasive Tumor Therapy Laboratory, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
Radiology. 2005 Aug;236(2):495-502. doi: 10.1148/radiol.2362040965.
To determine whether radiofrequency (RF)-induced heating can be correlated with background electrical conductivity in a controlled experimental phantom environment mimicking different background tissue electrical conductivities and to determine the potential electrical and physical basis for such a correlation by using computer modeling.
The effect of background tissue electrical conductivity on RF-induced heating was studied in a controlled system of 80 two-compartment agar phantoms (with inner wells of 0.3%, 1.0%, or 36.0% NaCl) with background conductivity that varied from 0.6% to 5.0% NaCl. Mathematical modeling of the relationship between electrical conductivity and temperatures 2 cm from the electrode (T2cm) was performed. Next, computer simulation of RF heating by using two-dimensional finite-element analysis (ETherm) was performed with parameters selected to approximate the agar phantoms. Resultant heating, in terms of both the T2cm and the distance of defined thermal isotherms from the electrode surface, was calculated and compared with the phantom data. Additionally, electrical and thermal profiles were determined by using the computer modeling data and correlated by using linear regression analysis.
For each inner compartment NaCl concentration, a negative exponential relationship was established between increased background NaCl concentration and the T2cm (R2= 0.64-0.78). Similar negative exponential relationships (r2 > 0.97%) were observed for the computer modeling. Correlation values (R2) between the computer and experimental data were 0.9, 0.9, and 0.55 for the 0.3%, 1.0%, and 36.0% inner NaCl concentrations, respectively. Plotting of the electrical field generated around the RF electrode identified the potential for a dramatic local change in electrical field distribution (ie, a second electrical peak ["E-peak"]) occurring at the interface between the two compartments of varied electrical background conductivity. Linear correlations between the E-peak and heating at T2cm (R2= 0.98-1.00) and the 50 degrees C isotherm (R2= 0.99-1.00) were established.
These results demonstrate the strong relationship between background tissue conductivity and RF heating and further explain electrical phenomena that occur in a two-compartment system.
在模拟不同背景组织电导率的可控实验模型环境中，确定射频（RF）诱导加热是否与背景电导率相关，并通过计算机建模确定这种相关性的潜在电学和物理基础。
在一个由80个双室琼脂模型组成的可控系统中（内孔含有0.3%、1.0%或36.0%的氯化钠），研究背景组织电导率对RF诱导加热的影响，背景电导率范围为0.6%至5.0%的氯化钠。对距离电极2 cm处的电导率与温度（T2cm）之间的关系进行了数学建模。接下来，使用二维有限元分析（ETherm）对RF加热进行计算机模拟，所选参数近似于琼脂模型。计算了以T2cm和定义的热等温线距电极表面的距离表示的加热结果，并与模型数据进行比较。此外，利用计算机建模数据确定了电学和热学剖面，并通过线性回归分析进行了相关性分析。
对于每个内室氯化钠浓度，背景氯化钠浓度增加与T2cm之间建立了负指数关系（R2 = 0.64 - 0.78）。计算机建模也观察到类似的负指数关系（r2 > 0.97%）。对于内氯化钠浓度为0.3%、1.0%和36.0%的情况，计算机与实验数据之间的相关值（R2）分别为0.9、0.9和0.55。绘制RF电极周围产生的电场图，确定了在电背景导率不同的两个隔室之间的界面处，电场分布可能发生剧烈局部变化（即第二个电峰 ["E峰"]）。建立了E峰与T2cm处的加热（R2 = 0.98 - 1.00）和50℃等温线处的加热（R2 = 0.99 - 1.00）之间的线性相关性。
这些结果证明了背景组织电导率与RF加热之间的密切关系，并进一步解释了双室系统中发生的电学现象。
