标题： 微泡增强高强度聚焦超声的建模 显示英文标题

标题： Modeling of Microbubble Enhanced High Intensity Focused Ultrasound

摘要： 在高强度聚焦超声（HIFU）场中，通过考虑在待消融肿瘤附近注入微气泡的影响，研究了目标处的热增强现象。 利用三维数值模型研究了气泡云与HIFU场之间的相互作用。 在组织或仿体介质中非线性超声波的传播使用固定网格上的可压缩纳维-斯托克斯方程进行建模，而微气泡的动力学和运动则作为离散奇点进行建模，并在拉格朗日框架中进行跟踪。 这两个模型相互耦合，使得声场和气泡相互影响。 通过在更长的时间尺度上求解传热方程来计算场中的温度升高。 通过进行没有微气泡的HIFU模拟，并将压力场和温度场与现有实验进行比较，对模型的可压缩连续体部分进行验证。 然后将耦合的欧拉-拉格朗日方法与现有仿体组织实验进行对比验证。 随后详细研究了微气泡增强热沉积的各种机制。 通过考虑初级超声波的衰减变化以及焦点区域增强热沉积的修改情况，研究了云中初始空隙率的影响。 最后，展示了微气泡云的大小及其在焦点区域的定位的影响，并讨论了这些参数对温度升高和温度峰值位置的影响。 显示英文摘要

摘要： Heat enhancement at the target in a High Intensity Focused Ultrasound (HIFU) field is investigated by considering the effects of the injection of microbubbles in the vicinity of the tumor to be ablated. The interaction between the bubble cloud and the HIFU field is investigated using a three-dimensional numerical model. The propagation of non-linear ultrasonic waves in the tissue or in a phantom medium is modeled using the compressible Navier-Stokes equations on a fixed grid, while the microbubbles dynamics and motion are modeled as discrete singularities, which are tracked in a Lagrangian framework. These two models are coupled to each other such that both the acoustic field and the bubbles influence each other. The temperature rise in the field is calculated by solving a heat transfer equation applied over a much longer time scale. The compressible continuum part of the model is validated by conducting HIFU simulation without microbubbles and comparing the pressure and temperature fields against available experiments. The coupled Eulerian-Lagrangian approach is then validated against existing experiments with a phantom tissue. The various mechanisms through which microbubbles enhance heat deposition are then examined in detail. The effects of the initial void fraction in the cloud are then sought by considering the changes in the attenuation of the primary ultrasonic wave and the modifications of the enhanced heat deposition in the focal region. Finally, the effects of the microbubble cloud size and its localization in the focal region are shown and the effects of these parameters in altering the temperature rise and the location of the temperature peak are discussed.