基于激光超声增强的聚焦磁声电成像新方法研究

The electrical characteristics of biological tissue are of great value to the basic research of life science and early diagnosis of major diseases. Magneto-acousto-electrical tomography, as the forefront of medical imaging, can quantitatively measure the electrical conductivities of tissue.However, the existing magneto-acousto-electrical tomography methods use non-focused piezoelectric ultrasonic transducer excitation, resulting in limited imaging resolution and detection sensitivity. Also, the electrical excitation brings the electromagnetic interference problem. This project presents a new method of enhancedfocused laser ultrasound induced magneto-acoustic imaging.In this project, the excitation and detection problems of laser generated focused ultrasoundon the new magneto-acoustic imaging method will be studied.The effects of focused ultrasound characteristics on the resolution of magneto-electroacoustic imaging will be investigated for different laser excitation parameters, lens parameters and opto-acoustic enhancement medium parameters.In order to improve the resolution and sensitivity of magneto-electro-acoustic imaging, the optimal focus of ultrasonic excitation parameters is proposed.In order to improve the resolution and sensitivity of magneto-acousto-electrical imaging, the excitation parameters of laser ultrasound will be optimized.Under the help of laser ultrasound enhancement technology, the resolution and sensitivity of traditional magneto-acousto-electrical will be increased by the new point to point fast reconstruction algorithms.A new high-resolution, high-sensitivity magnetic acoustic imaging method with independent intellectual property rights will be presented as an effective medical imaging technologyfor animal experiments, brain function imaging research.

生物组织的电学特性对生命科学和重大疾病的早期诊断基础研究具有重要价值，磁声电成像作为医学影像前沿技术，理论上能定量测量组织的电导率。但现有磁声电成像方法采用非聚焦压电超声换能器激励，导致成像分辨率和检测灵敏度受限，电学激励也带来了电磁干扰问题。本项目提出一种基于激光超声增强的聚焦磁声电成像新方法。研究该新型磁声电成像方法的激光聚焦超声激励检测理论，针对不同激光激励参数、透镜参数和光声增强介质参数研究聚焦超声特性，考察聚焦超声特性对磁声电成像分辨率的影响规律，找出有助于提高磁声电成像分辨率和灵敏度的最佳聚焦超声激励参数；结合研究的激光超声增强技术，突破传统磁声电成像方法分辨率和灵敏度低的问题，提出点点扫描激励的峰值检测快速重建算法。形成具有自主知识产权的新型高分辨率、高灵敏度的磁声电成像新方法，为动物实验、脑功能成像研究提供一种有效的医学影像技术。

激光聚焦超声具有非电学激励源、超声频率高、聚焦范围小等特点，不仅在医学治疗上有应用前景，也有望在医学成像中发挥重要作用。本项目将激光聚焦超声与磁声电成像方法相融合，提出一种基于激光超声增强的聚焦磁声电成像新方法。新型成像方法涉及激光诱导超声激励技术、诱导超声与磁场的耦合技术以及图像重建方法三个主要方面。项目首先围绕高光热转换效率的复合纳米薄膜材料，研究新型成像方法的激励检测理论，然后制备高光声转换效率的Au-PDMS复合薄膜和碳纳米材料复合薄膜，并对其声场特性进行研究和表征，得出，Au厚度在40 nm时，光声转换效率最优可达6 %；在Au厚度为35 nm，PDMS厚度为700 nm时，获得中心频率为37.5 GHz、声压为19 MPa光声响应；CB-PDMS复合材料膜层在光声响应上最高达到16.8MPa。最后利用研制的激光诱导超声换能器搭建新型磁声电实验平台，结合开发的非均匀声场磁声重建算法，实现仿体生物组织高分辨率磁声电成像。本项目研制的激光诱导超声换能器不仅可以在医学早期诊断领域实现高分辨率磁声电成像，而且在医学治疗方面，通过激光诱导超声换能器产生的高幅值负压对血栓实现空化溶栓治疗，对比研究了激光能量、换能器尺寸以及溶栓治疗时间对溶栓率的影响，在体外仿生血管中实现了3mg/min的溶栓速率。