基于超声调制的多频生物电阻抗层析成像新方法

Electrical impedance includes the rich messages of pathologies and physiologic activities. So, the measurement of bioimpedance has important significance for diagnosing the illness and evaluating the health condition. As one of the emerging hybrid imaging methods, ultrasound modulated electrical impedance tomography, which utilizes couplings between electric, ultrasound modalities, will perform higher spatial resolution than traditional electrical impedance tomography with more effective information. To measure the bioimpedance of tissues, considering the electrical properties of biological tissue will show significant changes as exciting frequencies changes, this project intends to research on a novel method of ultrasound modulated multi-frequency electrical impedance tomography. Based on the generation mechanism of acoustic-electric modulation effect in biological tissues, the basic model of acoustic-electric modulation effects will be improved, and the change of electrical parameters(conductivity and permitivity) induced by focused ultrasound will be investigated. The safe, fast and effective scanning method of focused ultrasound in biological tissues will be studied as well as error analysis from non-perfect ultrasound focusing scanning situation. Combining electrical properties of biological tissue, ultrasound modulated multi-frequency electrical impedance tomography which is suitable for biological tissue measurement will be reasearched on.By this method, high spatial resolution of conductivity distributions as well as permitivity distributions of biological tissues will be obtained. Based all of these,a high-resolution EIT system will be structured, which would provide a more precise visual tool for the measurement of bioimpedance.

生物体电阻抗信息的检测对疾病的诊断、健康状况的评估等具有重要的意义。基于超声调制的电阻抗层析成像方法，作为一种新型混合成像方法，通过电场、声场间的耦合增加有效信息量，有望提高传统的电阻抗层析成像的空间分辨率。本申请针对生物组织测量，结合生物组织电特性会随着激励频率的不同而呈现显著变化的特性，研究基于超声调制的多频电阻抗层析成像新方法。从生物组织介质声电调制的产生机理出发，改进现有的声电调制效应的基本模型，研究聚焦超声波导致聚焦点处电学参数（电导率、介电常数）的变化情况；研究生物组织介质超声的快速有效聚焦扫描方法，和非完美聚焦扫描情况下的误差分析；结合生物组织电特性，研究适合于生物组织测量的基于超声调制的多频电阻抗成像方法，在获得高空间分辨率的电导率分布的同时，重建高空间分辨率的介电常数分布，从而更全面的获得生物组织的阻抗信息，为生物组织电学参数测量提供更加准确的可视化工具。

电阻抗特性是生物体固有的电学特性，包含了丰富的病理、生理活动等信息。生物体电阻抗信息的检测对疾病的诊断、健康状况的评估等具有重要的意义。电阻抗层析成像是继形态、结构成像之后的新一代的无损伤功能成像方法，是当今生物医学工程学医学成像技术的重要研究课题之一。然而由于电阻抗层析成像的空间分辨率相对较低，在很大程度上限制了其实际应用。本项目针对生物组织测量，研究基于超声调制的电阻抗层析成像新方法，通过电场、声场间的耦合增加有效信息量，从而提高电阻抗层析成像的空间分辨率。国际上现有的声电调制效应的研究均是针对盐水或电解质溶液进行的，还没有针对生物组织进行研究的报道。课题组针对聚焦超声导致生物组织电导率变化的科学机理问题，基于固体力学理论，首次建立了生物组织声电效应模型，实现对生物组织多物理场耦合机理声电效应的研究。研究获取有效的额外信息的途径和图像重建方法，通过基于功率密度的线性化超声调制电阻抗层析成像图像重建方法、基于灵敏度矩阵的样本库的重建方法两种不同的思路实现了电导率的高分辨率重建，并在此基础上搭建了基于超声调制的电阻抗层析成像系统。基于超声调制的电阻抗层析成像是一种有潜力获得高空间分辨率重建的电阻抗成像新方法，它的成功应用将会扩展现有电阻抗成像的应用领域。