Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation
Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation
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DOI：
10.1118/1.2948388
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发表时间：
2008-08-01
期刊：
影响因子：
3.8
通讯作者：
Haemmerich, Dieter
中科院分区：
文献类型：
--
作者：
Schutt, David J.;Haemmerich, Dieter
目的：有限元法（FEM）模型通常用于模拟射频（RF）肿瘤消融。RF消融的现有FEM模型忽略了微血管灌注的温度依赖性效应，或者使用简化算法来实现该效应以降低计算复杂度。在该FEM建模研究中，作者比较了不同微血管灌注算法对肝组织中两种市售射频电极消融区尺寸的影响。他们还检查了组织类型和患者间灌注变化对消融区尺寸的影响。方法和材料：作者创建了内部冷却和多通道可扩张电极的FEM模型。向两个电极施加RF电压（分别持续12或15分钟），使得模型中的最高温度为105 ℃。使用三种先前报告的方法实现温度依赖性微血管灌注：在60 ℃以上停止，随着血管停滞程度增加灌注减少的标准一阶Arrhenius模型，以及包括由于充血而在消融区边界增加灌注的影响的Arrhenius模型。为了检查患者间差异的影响，使用灌注的基线和+/-1标准偏差值进行模拟。还改变了基线灌注，以模拟正常肝组织和坏死肝组织之间的差异。结果如下：与标准Arrhenius模型相比，在60 ℃以上灌注算法和更复杂Arrhenius模型下停止的消融区体积分别小70%和25%。消融区体积在模拟之间的差异高达175%和100%，其中在正常和坏死肝组织中分别使用灌注的-1和+1标准差值。结论：在射频消融的有限元模型中，微血管灌注算法的选择对最终消融区尺寸有显著影响。作者还发现，基线组织灌注的患者间差异和肝硬化导致的灌注减少对消融区尺寸有相当大的影响。(c)2008年美国医学物理学家协会。
Purpose: Finite element method (FEM) models are commonly used to simulate radio frequency (RF) tumor ablation. Prior FEM models of RF ablation have either ignored the temperature dependent effect of microvascular perfusion, or implemented the effect using simplified algorithms to reduce computational complexity. In this FEM modeling study, the authors compared the effect of different microvascular perfusion algorithms on ablation zone dimensions with two commercial RF electrodes in hepatic tissue. They also examine the effect of tissue type and inter-patient variation of perfusion on ablation zone dimensions. Methods and Materials: The authors created FEM models of an internally cooled and multi-tined expandable electrode. RF voltage was applied to both electrodes (for 12 or 15 min, respectively) such that the maximum temperature in the model was 105 degrees C. Temperature dependent microvascular perfusion was implemented using three previously reported methodologies: cessation above 60 degrees C, a standard first-order Arrhenius model with decreasing perfusion with increasing degree of vascular stasis, and an Arrhenius model that included the effects of increasing perfusion at the ablation zone boundary due to hyperemia. To examine the effects of interpatient variation, simulations were performed with base line and +/- 1 standard deviation values of perfusion. The base line perfusion was also varied to simulate the difference between normal and cirrhotic liver tissue. Results: The ablation zone volumes with the cessation above 60 degrees C perfusion algorithm and with the more complex Arrhenius model were up to 70% and 25% smaller, respectively, compared to the standard Arrhenius model. Ablation zone volumes were up to similar to 175% and similar to 100% different between the simulations where -1 and +1 standard deviation values of perfusion were used in normal and cirrhotic liver tissue, respectively. Conclusions: The choice of microvascular perfusion algorithm has significant effects on final ablation zone dimensions in FEM models of RF ablation. The authors also found that both interpatient variation in base line tissue perfusion and the reduction in perfusion due to cirrhosis have considerable effect on ablation zone dimensions. (c) 2008 American Association of Physicists in Medicine.