脉冲超声辅助热疗治疗皮下肿瘤的数值研究
Pulsed Ultrasound Assisted Thermo-therapy for Subsurface Tumor Ablation: A numerical investigation
摘要：
高强度聚焦超声（HIFU）具有无创、穿透深度大等特点，是一种很有前途的热消融和热疗治疗方法。有效的HIFU热治疗需要能够准确地预测靶组织中的温升和相应的热剂量分布。我们报告了一个参数的数值研究的热响应和相应的热剂量在生物组织中响应超声。我们比较了两层、三层和七层组织模型的预测结果与占空比为0.6和0.9的超声诱导加热。此外，考虑了两种肿瘤尺寸和换能器功率（10 W和15 W）。将非均匀Helmholtz方程与Penne的生物热方程相结合，预测脉冲超声的加热响应。使用累积等效分钟（CEM）热剂量函数计算坏死病灶大小。用琼脂基组织模型进行体外实验，作为数值结果的初步验证。使用七层模型进行的模拟预测的峰值压力幅度比三层模型低33.5%。当等效声处理时间一定时，随着超声脉冲宽度的减小，对应的峰值温度和温升速率减小。脉冲超声波导致增加体积的坏死病变的等效时间的超声处理。这项研究的结果突出了HIFU诱导的加热对目标几何形状和声学特性的依赖性，并有助于指导选择合适的超声暴露参数进行进一步研究。
英文摘要：
High Intensity Focused Ultrasound (HIFU) is a promising therapy for thermal ablation and hyperthermia, characterised by it noninvasiveness, high penetration depth. Effective HIFU thermo-therapy requires the ability to accurately predict temperature elevation and corresponding thermal dose distribution in target tissues. We report a parametric numerical study of the thermal response and corresponding of thermal dose in a bio-tissue in response to ultrasound. We compared the predictions of tissue models with two, three and seven layers, to ultrasound induced heating at duty cycles ranging from 0.6 and 0.9. Further, two tumor sizes and transducer powers (10 W and 15 W) were considered. Inhomogeneous Helmholtz equation was coupled with Penne's bioheat equation to predict heating in response to pulsed ultrasound. Necrotic lesion size was calculated using the cumulative equivalent minute (CEM) thermal dose function. In-vitro experiments were performed with agar-based tissue phantoms as a preliminary validation of the numerical results. The simulations conducted with the seven layered model predicted up to 33.5% lower peak pressure amplitude than the three-layered model. As the ultrasound pulse width decreased with the equivalent sonication time fixed, the corresponding magnitude of the peak temperature and the rate of temperature rise decreased. Pulsed ultrasound resulted in increased the volume of necrotic lesions for equivalent time of sonication. The findings of this study highlight the dependence of HIFU-induced heating on target geometry and acoustic properties, and could help guide the choice of suitable ultrasound exposure parameters for further studies.
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