【作者】 肖哲；

【导师】 郁道银；

【作者基本信息】 天津大学 ， 光学工程， 2006， 硕士

【摘要】 医用超声内窥镜是电子内窥镜技术与超声传感技术、微机电技术、现代计算机技术等高新技术的不断发展和融合的产物,是当前应用前景非常广阔的医疗仪器。内窥镜超声成像系统以电子内窥镜系统为基础,将超声探头经由电子内窥镜活检通道伸入体腔、接近目标器官,由微型电动机驱动超声探头实现扇面扫描,获得消化器官管壁各个断层的组织学特征。与电子内窥镜相比,提高了早期病变诊断的能力。与体外超声比较,探头与器官间距离短,避免了脂肪、体腔内气体对成像的影响,获得的图像信息要比体表上获得的扫描信息准确详细。内窥镜超声成像系统关键技术的研究主要包括:超声探头激励电路、回波信号接收处理电路、同步控制电路三个部分的内容。本文根据超声成像系统的要求完成了三个部分电路的设计与实现;同时,根据对医用内窥镜超声成像的清晰度、分辨率和保真度的要求进行分析,并提出了新的提高超声图像质量的数字化方法。超声波的发射是由压电换能器完成的。激发电路的功能即是产生瞬时高压脉冲,激励超声换能器发射超声波。激发电路包括同步控制脉冲产生电路、激发主电路和换能器的调谐匹配电路,这三部分电路控制超声换能器按照一定的频率高效的发射超声波。回波处理电路用于检测由人体组织反射的超声信息,对转换成的电信号进行解调输出。回波处理电路包括放大电路、增益补偿电路、检波、滤波及A/D转换电路。解调出的信号进行A/D转换,输出图像的扫描线数字信号,经FIFO缓存后,数字信号由PCI图像采集卡进入计算机内存。现场可编程逻辑阵列(FPGA)作为核心控制模块完成对数据传输和相关电路及芯片的控制,主要实现了对超声波激发、A/D转换以及成像部分同步控制。根据各部分电路在系统中的功能,详细地介绍了FPGA产生外部电路控制逻辑和数字信号处理的方法,并给出了相关的实验波形图和硬件系统的整体调试结果。系统的各电路性能均得到实验验证,达到了医用超声内窥镜探头驱动控制系统的各项指标要求,并实现了显示512×512大小的超声扫描图像的要求。最后,分析了系统的噪声来源,总结了系统的特点,并提出了改善超声成像质量的措施和方法。更多还原

【Abstract】 Endoscopic Ultrasonography System (EUS) is a nonsurgical medical evaluation that has been proven effective for diagnosing gastrointestinal diseases. EUS will be a widely used and reliable endosonography instruments in the world. Endoscopic Ultrasonography, or EUS, combines the medical technique of endoscopies with ultrasound technology and modern computer technology. EUS uses a flexible tube called an endoscope, which works like a periscope. The doctor inserts this tube into the digestive tract through the mouth or the rectum. This state-of-the-art combination allows the doctor to examine internal organs not only by the tissue surface, but also by ultrasonic tomography images which can show the pathological changes under tissue surface, and photograph and videotape the findings.The key technologies of ultrasonic imaging system are emission circuit, receiving circuit and synchronous control circuit. On the basis of ultrasonic imaging system, we have concretely complemented the circuits design and implementation. In addition, according to the definition, resolution factor and fidelity factor requirements of ultrasonic imaging system, I put forward new methods for increasing the SNR of ultrasonic images.The ultrasonic is emitted from a piezoelectric sensor. The function of emission circuits is to produce instantaneous high voltage plus, inspiriting piezoelectric sensor to transmit ultrasonic. Emission circuits include a creation circuit of synchronous pulse, the basic circuit for emission and tuned coupled circuit, which control the piezoelectric sensor transmitting ultrasonic according to a certain frequency.Receiving circuits detect the wave reflected by human tissue and output electric signal that has been demodulated. The receiving circuit is composed of amplification circuit, variable gain amplification circuit, demodulation circuit, filter circuit and A/D translation circuit. The output of emission circuit is digital signal of scanning line. After buffer storage, the digital signal is send into the computer through PCI card.A FPGA is used as the kernel module to control the data transferring、related circuit and chips working, accomplishing the synchronous control among the ultrasonic emission、receiving、analog-to-digital conversion and ultrasonic imaging. On the basis of different functions of these circuits, I concretely introduce the methods of digital processing and how the FPGA implements the control logic. In addition, the correlative experimental oscillogram and the debugging results of hardware system are offered.The performance of each circuit has been verified by experiments and has been achieved the norms for Endoscopic Ultrasonography System. The image size is 512×512, which meets the demand of this system. In the end, noises of the whole system are summarized and further work for improving the imaging quality is indicated.更多还原