Faculty of Civil Engineering, RWTH Aachen University, Aachen, Germany.
Philips Research, Eindhoven, The Netherlands.
Int J Hyperthermia. 2021;38(1):95-104. doi: 10.1080/02656736.2020.1866217.
Computer simulations of hepatic radio-frequency ablation (RFA) were performed to: () determine the dependence of the vessel wall heat transfer coefficient on geometrical parameters; () study the conditions required for the occurrence of the directional effect of blood; and () 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.
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.
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.
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.
进行肝脏射频消融（RFA）的计算机模拟，以：（）确定血管壁热传递系数对几何参数的依赖性；（）研究发生血液定向效应的条件；以及（）在考虑血液凝固的情况下根据其对热损伤的影响对血管进行分类。由此获得的信息支持开发多尺度生物传热模型，以更准确地预测血管附近肝脏 RFA 结果。
模拟几何形状由健康组织、肿瘤组织、单极射频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结构的参数。开发并测试了一种将血液凝固影响纳入模拟的简单新颖方法。
得到了血管壁热传递系数对几何参数的依赖的闭合形式表达式。对于半径为 0.4-0.5 毫米的血管，发现热损伤存在定向效应。小于 0.4 毫米的半径会导致血液凝固阻塞血流。
热传递系数的闭合形式表达式可用于 RFA 模型以加快计算速度。确定了发生热损伤定向效应的血管半径条件。这些条件允许对血管进行分类。因此，可以对这些血管类别使用不同的热方程近似。
