用于聚焦超声热疗过程实时监测的电阻抗技术研究

High Intensity Focused Ultrasound therapy technique has been clinically approved that it provides a new hope and option of survive to cancer patients. Real-time monitoring technique is required to grantee therapy quality. MRI and B-scan are two kinds of image techniques that have been used to monitor the lesion formation via temperature measurement and time parameters, but they both have various problems like expensive cost, compatibility issue and wrong-judgment, etc. Electrical Impedance Tomography technique has advantages such as cost-effective, safety, fast-speed, non-destructive, as well as good temperature sensitivity. The temperature-impedance variation factor (TIVF) of in-vitro tissue shows sharp change when tissue coagulation happens, which means, compared to those temperature based quality assurance techniques, the TIVF of impedance technique has great potential to be used as solid and direct indication for the on-set of tissue coagulation and further more to assure the therapy quality. The proposal will investigate the electrical impedance technique used to real-time monitor hyperthermia therapy, based on our research results over the past 20 years. Related issues will be thoroughly investigated, including: to develop a new micro-sized impedance probe with 4 rings of electrodes and a thermocouple on the tip, and then use the probe to measure in vivo tissue impedivity and its variation during hyperthermia with minimal invasion; to develop a high-precision, fast speed, wide-band electrical impedance measurement system for impedance data collection; to develop an algorithm for real part and imaginary part image reconstruction with regional high-resolution; and finally validate the effectiveness of impedance data and impedance image used to monitor HIFU treatment via in vivo animal experiments. The proposed research will make significant scientific contribution as well as great social benefit and economic value.

聚焦超声热疗技术已被临床证明能为肿瘤患者提供一种新的治疗选择和生存希望，但需对热疗过程进行实时监测以确保治疗质量。MRI和B超通过检测温度和时间来保证焦域的形成，存在误判、费用高和兼容性等问题。电阻抗技术具有经济、安全、快速、无创等优点，对温升具有良好敏感性，电阻抗-温度变化系数在离体组织凝固性坏死时发生显著突变，能够作为组织焦域形成的直接证据，相比基于温度的热疗监测方法能更有效保证治疗效果。 本申请拟在申请人多年研究成果基础上，研究用于热疗过程实时监测的电阻抗技术，包括研制一种活体组织电特性测试微创四环电极探针，进行实验研究，总结热疗过程中活体组织电特性的变化规律；研制高精度、快速、多频率的电阻抗数据采集系统；研究具有局部高分辨率的电阻抗实部与虚部图像重建算法；最终通过电阻抗数据及图像对热疗过程中组织凝固性坏死的发生和温度变化进行实时检测，确保热疗效果。具有重要科学意义和社会经济价值。

聚焦超声 (High Intensity Focused Ultrasound, HIFU) 热疗过程监测是保证治疗质量的关键。临床上因为治疗不彻底、肿瘤复发的情况时有发生，迫切需要简便易行、可靠有效的治疗质量监测方法。. 生物组织电阻抗特性对热疗过程的电导率变化表现出非常好的敏感性。本项目研究用于聚焦超声热疗过程监测的电阻抗技术，主要成果如下：..成功研制了一种微型电阻抗探针，发现生物电阻抗技术能够用于动物组织新鲜度的测试，提出了判断动物组织离体时间/新鲜度的量化指标；提出一种可以实时测量并实际可以使用的细胞凋亡的判断依据----1MHz /5kHz阻抗比，对细胞凋亡的发生具有良好的敏感性，具有重要临床意义。..解决高精度信号源、信号调理电路等问题，设计实现了一套高精度多频率的快速电阻抗数据采集系统。实验测试结果表明，该系统性能稳定，在 1kHz to 1MHz的频率范围内信噪比(SNR)优于73dB、重复性优于0.4%，所有性能测试所使用的激励电流幅值均小于0.4mA，远低于人体的安全电流5mA。..研究出一种基于感兴趣区域的具有局部高分辨率的 EIT 图像重建的理论与算法，能在不增加电极数目的条件下提高感兴趣区域内的图像分辨率；提出最优参考电导率的概念，通过拟合方法求得的非均匀参考场的最优参考电导率，比传统的由连续相电导率为参考电导率的图像重建方案，重建结果更准确。..实现了基于CT图像的EIT三维建模及有限元仿真和图像重建。研究了一种具有普适性的从CT图像提取胸腔与主要器官轮廓的算法，能快速从多层CT图像准确提取人体胸腔和主要脏器的轮廓，建立三维人体躯干模型，进行三维有限元仿真和图像重建。仿真实验研究表明真实人体三维模型上的图像重建比传统的三维圆柱体、二维圆域、二维胸腔轮廓上的图像重建都更为准确。..实验研究。用所研制的EIT系统观测人体呼吸过程，获得人体呼吸过程的图像，证明所研制的EIT系统安全可靠，能够用于人体监测。用所研制的EIT系统观测离体猪肉组织的热疗实验，证明EIT图像对热疗过程中温升引起的电阻抗特性变化敏感。