HIFU治疗中靶组织粘弹性-温度的时变规律与凝固性坏死预测研究

High intensity focused ultrasound (HIFU) is a noninvasive technology for treatment of cancer. Real-time intraoperative monitoring is critical to HIFU treatment. As traditional single-parameter monitoring means, ultrasound imaging or MR temperature is low sensitive and specific for coagulation necrosis. So it is easy to cause excessive or insufficient HIFU radiation. Viscoelastic imaging is a hotspot as its high contrast in HIFU evaluation. Especially, the viscoelastic imaging based on shear waves shows promising potential. We assume the temperature changes can be as the stimulation to tissue environment, and viscoelasticity changes as the responses, then the viscoelasticity and temperature changes with time will follow inherent laws. It is likely to provide clues for more sensitive and robust sense of coagulation necrosis in advance. As a combination of ultrasound and MR temperature monitoring, this investigation is expected to avoid the defects caused by single monitoring pattern. Accordingly, this study proposed is to solve the following problems by the simulation and phantom experiment: 1) find out the synchronous change laws of viscoelasticity and temperature with time, and to extract the effective indexes for evaluation and prediction of coagulation necrosis; 2) real-time estimation of viscoelastic distribution based on shear waves. The final goal is to provide a scientific basis for forming accurate coagulation necrosis in target area and improve the effect of HIFU treatment.

高强度聚焦超声(HIFU)是前景广阔的无创肿瘤治疗新技术，其术中监控对手术成败影响重大。作为目前主要的监控手段，单一的超声显像或MR温度监控存在对凝固性坏死敏感度低、特异性差等问题。具有高对比度的粘弹性成像是当前研究热点，特别是基于剪切波的粘弹性成像在HIFU疗效评估中展示出良好前景。我们假设温度变化是对组织环境的刺激，而粘弹性变化是组织对环境变化的响应，那么粘弹性与温度变化在时间轴上存在固有规律可循，很可能为更灵敏、鲁棒地提前感知凝固性坏死提供线索。这将是超声和MR温度监控的有机结合，有望避免这两种单一监控模式的缺陷。据此，本课题拟通过仿真和仿体实验解决以下问题：1）探明靶区粘弹性和温度在时间轴上的同步变化规律，并从中提取有效的评估及预测指标；2）基于剪切波的粘弹性分布实时计算。课题的研究期望为实时评估靶区组织损伤程度及凝固性坏死预测提供科学依据，进而提高HIFU治疗效果。

高强度聚焦超声是前景广阔的无创肿瘤治疗新技术，其术中监控对手术成败影响重大。作为目前主要监控手段，单一的超声显像或 MR 温度监控存在对凝固性坏死敏感度低、特异性差等问题。对此，我们研究了这两物理量之间的时变规律及测量技术以寻求更准确的术中监控方法。首先，制备了本研究所需的仿生物组织透明体模，其性能有利于对受损区域进行动态、实时的观察；然后，研究高强度聚焦超声辐照体模过程中温度的时变特点，提取出“激励时间-温度曲线”，观测了靶区温度在时间轴上的变化趋势；随后我们研究了高强度聚焦超声辐照体模过程中的弹性时变特点，提取出“激励时间-弹性曲线”，探明了靶区弹性在时间轴上的变化特点；进一步，通过研究“激励时间-弹性与温度曲线”，对凝固性坏死发生时间点进行规律分析；我们还研究了凝固性坏死损伤图像检测（分割与运动估计）方法及自适应粘弹性成像方法，提出了基于可变滤波器长度的自适应超声弹性成像方法、基于可变窗数值优化算法的自适应超声弹性成像方法和基于动态孔径控制的自适应超声弹性成像方法，获得了一些研究成果。本课题的研究结果为实时评估靶区组织损伤程度及凝固性坏死预测提供科学依据，以提高高强度聚焦超声治疗的术中监控技术水平。