Abstract

Purpose

Computer simulations of hepatic radio-frequency ablation (RFA) were performed to: (i) determine the dependence of the vessel wall heat transfer coefficient on geometrical parameters; (ii) study the conditions required for the occurrence of the directional effect of blood; and (iii) classify blood vessels according to their effect on the thermal lesion while considering blood coagulation. The information thus obtained supports the development of a multi-scale bio-heat model tailored for more accurate prediction of hepatic RFA outcomes in the vicinity of blood vessels.

Materials and methods

The simulation geometry consisted of healthy tissue, tumor tissue, a mono-polar RF-needle, and a single cylindrical blood vessel. The geometrical parameters of interest were the RF-needle active length and those describing blood vessel configuration. A simple, novel method to incorporate the effects of blood coagulation into the simulation was developed and tested.

Results

A closed form expression giving the dependence of the vessel wall heat transfer coefficient on geometrical parameters was obtained. Directional effects on the thermal lesion were found to occur for blood vessel radii between 0.4 mm and 0.5 mm. Below 0.4 mm blood coagulation blocked the flow.

Conclusions

The closed form expression for the heat transfer coefficient can be used in models of RFA to speed up computation. The conditions on vessel radii required for the occurrence of directional effects on the thermal lesion were determined. These conditions allow the classification of blood vessels. Different approximations to the thermal equation can thus be used for these vessel classes.

中文翻译：

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肝射频消融中血管冷却和凝血功能的模拟研究

摘要

目的

进行肝射频消融（RFA）的计算机模拟是：（i）确定血管壁传热系数对几何参数的依赖性；（ii）研究发生血液定向作用所需的条件；（iii）在考虑凝血的同时，根据其对热损伤的作用对血管进行分类。如此获得的信息支持了多尺度生物热模型的开发，该模型专为更准确地预测血管附近的肝RFA结果而设计。

材料和方法

模拟几何结构由健康组织，肿瘤组织，单极RF针和单个圆柱形血管组成。感兴趣的几何参数是RF针的有效长度和描述血管构造的参数。开发并测试了一种简单，新颖的方法，将凝血作用纳入仿真。

结果

获得了给出容器壁传热系数对几何参数的依赖性的闭合形式表达式。发现在0.4 mm至0.5 mm的血管半径内会发生热损伤的方向性影响。低于0.4毫米的血液凝结会阻塞血流。

结论

传热系数的闭合形式表达式可用于RFA模型中，以加快计算速度。确定了对热损伤产生方向性影响所需的血管半径条件。这些条件允许对血管进行分类。因此，对于这些容器类别，可以使用热方程的不同近似值。