Liu Z, Ahmed M, Sabir A, Humphries S, Goldberg S N
Department of Radiology, Beth Israel Deaconess Medical Center-Harvard Medical School, Boston, MA 02215, USA.
Int J Hyperthermia. 2007 Feb;23(1):49-58. doi: 10.1080/02656730601094415.
To use an established computer simulation model of radiofrequency (RF) ablation to further characterize the effect of varied perfusion on RF heating for commonly used RF durations and electrode types, and different tumor sizes.
Computer simulation of RF heating using 2-D and 3-D finite element analysis (Etherm) was performed. Simulated RF application was systematically modeled on clinically relevant application parameters for a range of inner tumor perfusion (0-5 kg/m3-s) and outer normal surrounding tissue perfusion (0-5 kg/m3-s) for internally cooled 3-cm single and 2.5-cm cluster electrodes over a range of tumor diameters (2-5 cm), and RF application times (5-60 min; n = 4618 simulations). Tissue heating patterns and the time required to heat the entire tumor +/- a 5-mm margin to > 50 degrees C were assessed. Three-dimensional surface response contours were generated, and linear and higher order curve-fitting was performed.
For both electrodes, increasing overall tissue perfusion exponentially decreased the overall distance of the 50 degrees C isotherm (R2 = 0.94). Simultaneously, increasing overall perfusion exponentially decreased the time required to achieve thermal equilibrium (R2 = 0.94). Furthermore, the relative effect of inner and outer perfusion varied with increasing tumor size. For smaller tumors (2 cm diameter, 3-cm single; 2-3 cm diameter, cluster), the ability and time to achieve tumor ablation was largely determined by the outer tissue perfusion value. However, for larger tumors (4-5 cm diameter single; 5 cm diameter cluster), inner tumor perfusion had the predominant effect.
Computer modeling demonstrates that perfusion reduces both RF coagulation and the time to achieve thermal equilibrium. These results further show the importance of considering not only tumor perfusion, but also size (in addition to background tissue perfusion) when attempting to predict the effect of perfusion on RF heating and ablation times.
使用已建立的射频（RF）消融计算机模拟模型，进一步描述在常用的射频持续时间、电极类型以及不同肿瘤大小情况下，变化的灌注对射频加热效果的影响。
采用二维和三维有限元分析（Etherm）对射频加热进行计算机模拟。针对一系列内部肿瘤灌注（0 - 5 kg/m³·s）和外部正常周围组织灌注（0 - 5 kg/m³·s），在一系列肿瘤直径（2 - 5 cm）以及射频施加时间（5 - 60分钟；共4618次模拟）的情况下，对内部冷却的3 cm单电极和2.5 cm簇状电极，依据临床相关应用参数系统地建立模拟射频施加模型。评估组织加热模式以及将整个肿瘤及其±5 mm边缘加热至>50摄氏度所需的时间。生成三维表面响应等高线，并进行线性和高阶曲线拟合。
对于两种电极，增加整体组织灌注均会使50摄氏度等温线的整体距离呈指数下降（R² = 0.94）。同时，增加整体灌注会使达到热平衡所需的时间呈指数下降（R² = 0.94）。此外，内部和外部灌注的相对影响随肿瘤大小增加而变化。对于较小的肿瘤（直径2 cm，单电极3 cm；直径2 - 3 cm，簇状电极），实现肿瘤消融的能力和时间很大程度上由外部组织灌注值决定。然而，对于较大的肿瘤（直径4 - 5 cm，单电极；直径5 cm，簇状电极），内部肿瘤灌注起主要作用。
计算机建模表明灌注会降低射频凝固以及达到热平衡的时间。这些结果进一步表明，在试图预测灌注对射频加热和消融时间的影响时，不仅要考虑肿瘤灌注，还需考虑肿瘤大小（以及背景组织灌注）的重要性。
