【作者】 孙平；

【导师】 王高峰；

【作者基本信息】 武汉大学 ， 微电子学与固体电子学， 2009， 博士

【摘要】 医学超声诊断设备,由于其具有无创、无痛、方便有效、显示直观、成本低廉等优点,被广泛的使用于医学诊断的各个领域。频率大于20 MHz的高频超声,能够提供更高的图像分辨率,因此特别适用于显示精细的结构,可用于探测人体的眼睛、皮肤和血管等器官,也可用于对小动物如老鼠、斑马鱼等的成像。当前,研究和制作性能良好的高频超声传感器和高频超声成像系统仍是一项非常重要的、具有挑战性的工作。本文首先设计和制作了两种不同类别的35 MHz高频超声传感器。其中用新的铌酸铅铟-铌镁酸铅-钛酸铅(PIN-PMN-PT)材料制作的PIN-PMN-PT超声单阵元传感器具有比传统铌镁酸铅-钛酸铅(PMN-PT)超声传感器更高的温度稳定性,并且可以在更高的电压下工作。用PMN-PT\Epoxy 1-3复合材料制作的PMN-PT\Epoxy 1-3复合超声单阵元传感器具有比传统铌镁酸铅-钛酸铅(PMN-PT)超声传感器更高的机电耦合系统和更低的声阻抗特性。其次,本文设计和制作了用于高频超声传感器阵列的高频医学超声成像系统。该系统具有64个通道,采用了多个高速A/D转换芯片,能实现64通道12位精度超声接收数据的高速采集(160MSPS)。系统中设有多个强大的现场可编程门阵列(FPGA)芯片和一个大规模并行数字信号处理器阵列(MPPA),可以完成数据的缓存、系统的控制,并实现高速的数字信号处理。系统中还使用了GPIO接口和PCI EXPRESS接口,实现了高速的数据传输(200MBPS以上)。此外,本文还对系统的软件进行了开发。整个系统采用了模块化的结构,因此具有良好的灵活性和适应性,可以便利的实现系统的调整和升级。再次,本文研究了超声波波束形成技术,讨论了超声波波束发射和接收算法和延迟技术。在单片FPGA中实现了64通道的数字式超声发射,并提出了三种基于本文硬件系统的超声波波束接收算法的实现方案。其中FPGA+MPPA的实现方案可实现数据的高效处理,结合使用FIR插值滤波的方法可将接收延迟精度提高到1 ns以内。最后,本文对设计和制作的高频超声传感器以及高频医学超声成像系统进行了测试。对PIN-PMN-PT超声传感器和PMN-PT\Epoxy 1-3复合超声传感器的测试结果表明,这两种传感器的性能良好,工作频率均在30 MHz以上,插入损耗在20db一下,可以用于高频超声成像。对高频医学超声成像系统的测试结果表明,该系统硬件部分能够完成64通道超声信号的发射、接收和数据采集,利用MPPA-Am2045芯片可以实现高精度的数据延迟,实现了高频医学超声成像系统的基本功能。更多还原

【Abstract】 Medical ultrasound diagnostic instruments, because of its noninvasive, efficacy and low cost, are widely used in clinic. High-frequency (>20 MHz) ultrasound has demonstrated high spatial resolution on the submillimeter level, and can be applied to ophthalmology, dermatology, small animal imaging, and intravascular imaging. However, to get a high quality imaging, the development of high-frequency ultrasound transducers and high-frequency ultrasound imaging system is essential and challenging.In this thesis, two different types of high-frequency ultrasound single-element transducer:PIN-PMN-PT single-element transducer and PMN-PT\Epoxy 1-3 composite single-element transducer, are designed and fabricated. While the PIN-PMN-PT transducer reveals better thermal stability than PMN-PT transducer, the PMN-PT\Epoxy 1-3 composite transducer has lower acoustic impedance and higher electromechanical coupling coefficient.A high-frequency medical ultrasound imaging system for high-frequency ultrasonic arrays has been developed. The system can handle up to 64-element array transducers and excite 64 channels and receive simultaneously at 160 MHz sampling frequency with 12-bit precision. Field programmable gate array (FPGA) and massively parallel processor array (MPPA) are used for high-speed digital signal parallely processing. GPIO and PCI EXPRESS physical interface are used for high-speed data transfer. In addition, the frame of software system is built. By using modular structure, the system has highly flexibility and adaptability, can be easily extended and upgraded.Furthermore, the ultrasound beamforming technique is studied; the arithmetic for ultrasound transmition and receiving is discussed. Multi-channel digital ultrasound transmit is implemented in a Field programmable gate array (FPGA), and three proposal for the implementation of ultrasound receive beamforming are put forward. Among the three proposals, the architecture based on FPGA and MPPA reveals good performance, the delay can be reduced under 1 ns by using a FIR interpolation filter.Finally the testing results of the fabricated ultrasound transducers and imaging system are given. Results show that both the PIN-PMN-PT transducer and PMN-PT\Epoxy 1-3 composite transducer have superior performance and can be used for high-frequency ultrasound imaging. Results also show that the imaging system can successfully realize the multi-channel ultrasound transmit, receiving and signal acquisition, and the digital beamforming can achieve a high-speed fine delay.更多还原