高强度聚焦超声（HIFU）是一种极具潜力的无创治疗技术，已在临床治疗和设备研制方面得到了广泛应用与关注，但HIFU换能器电阻抗动态变化导致的功率传输问题严重影响了HIFU治疗的有效性和安全性。目前对HIFU换能器电阻抗在工作状态下的的变化规律还不明确，尚缺少一种能有效消除HIFU换能器电阻抗变化影响的阻抗匹配方法。本项目从研究HIFU换能器工作状态下电阻抗动态变化的特性及规律出发，将最小失配网络理论引入至超声换能器电阻抗匹配网络，拟结合最优化算法和简化实频法宽带阻抗匹配网络理论，提出HIFU换能器电阻抗变化下的最小失配网络优化策略与设计理论，重点研究HIFU换能器电阻抗在线测量方法、电阻抗变化特性及规律和最小失配网络的最优化设计理论三方面内容，获得一种对HIFU换能器电阻抗变化不敏感的阻抗匹配网络，以提高超声功率传输的动态稳定性，为下一代更高效、更安全的HIFU治疗系统提供理论支撑。

High-intensity focused ultrasound (HIFU) therapy is a promising non-invasive treatment technology emerging in recent years. Our country is a world leader in HIFU treatment device development and clinical application. However, the power transmission problem caused by dynamic variation of HIFU transducer's impedance influences the efficiency and safety of HIFU therapy seriously. Frequency tracking and automatic impedance matching can not be applied on HIFU transducer by operating frequency variation and matching speed. There’s lacking an impedance matching method which eliminates the influence of impedance variation. Combining with our preliminary research on this subject, we import first time the minimum mismatch network theory into the impedance matching design of ultrasound transducer. Optimization algorithm and wideband impedance matching design method are combined to propose the minimum mismatching design theory for HIFU transducer with varying impedance. Online electrical impedance measurement method of HIFU transducer, impedance variation characteristics and regulation, optimization design theory for minimum mismatch network will be studied in this project. An impedance matching network insensible to variation of HIFU transducer's impedance will be obtained for improving the dynamic stability of ultrasound power transmission. This study will provide theoretical support for more efficient and safe HIFU therapy system.