【作者】 温世杰；

【导师】 郁道银；

【作者基本信息】 天津大学 ， 光学工程， 2009， 博士

【摘要】 超声内窥镜通过电子内窥镜的活检通道将微型超声扫描探头送入人体,在内窥镜观察体内器官内腔粘膜面的同时,超声扫描探头获取人体内脏器官壁的断层图像,发现其中的早期癌变和微小肿瘤,是目前诊断人体内脏器官病变的最佳方法。本文针对国外超声内窥镜产品的不足,首次提出了微型超声电机前置驱动超声换能器旋转的超声内窥镜设计方案,即超声电机与超声换能器固为一体,形成微型超声旋转扫描探头,然后通过电子内窥镜的活检通道进入人体内腔进行旋转扫描成像。该设计方案在获得清晰的人体内腔断层图像的同时,大大延长了仪器的使用寿命。本文的主要工作有:1、根据电子内窥镜活检通道的尺寸和结构,设计了由微型超声电机和微型超声换能器组成的微型超声旋转扫描探头,探头的直径为1.8 mm,不可弯曲长度为14 mm,扫描频率为5帧/秒。经实验证明,超声探头转速稳定,在实验室的条件下,可连续旋转一月以上。2、为了克服微型超声探头对换能器发射功率的限制,增强超声信号的信噪比,进而提高超声内窥镜系统的探测深度和成像质量,设计和研制了数字式超声成像系统,主要包括以下几方面的内容:a)将广泛应用于雷达系统中的“编码激励技术”引入到超声内窥镜成像系统中。该技术采用长编码信号激励超声换能器,提高了超声信号的发射功率,突破了换能器尺寸对发射功率的限制,有效地增强了回波信号的信噪比。b)借鉴软件无线电中的“数字下变频”技术,设计了由高速采样电路、FPGA(现场可编程门阵列)信号处理电路和SRAM图像存储电路组成的数字接收系统。该系统将模数转换推进到接收电路的最前端,在中频段完成回波信号采样,使得超声成像系统中,除发射和放大电路外的所有信号处理工作完全由数字电路实现,大大提高了系统的信噪比和稳定性。c)采用Cypress公司EZ-USB FX2系列的USB2.0接口芯片,设计了超声图像的高速实时传输电路,并编写了基于USB2.0的超声图像实时显示软件。USB2.0接口电路将FPGA输出的图像数据传送到计算机内存,然后由显示软件读取,实现超声图像的实时显示与存储。3、利用设计的电路搭建了一套数字超声内窥镜成像实验系统,实现了超声换能器的编码激励,从玻璃杯壁反射的回波信号具备编码特征,且与MATLAB仿真的结果一致。同时,利用该实验系统还获得了清晰的玻璃杯壁旋转扫描图像,验证了系统设计的正确性。更多还原

【Abstract】 The ultrasonic endoscope, which combines an electronic endoscope and a miniultrasonic imaging system, sends a micro ultrasonic probe into coelom through thebiopsy channel of the electronic endoscope. In this way, the ultrasonic endoscope canget pictures of the alimentary canal mucosal surface and images of the full histologyof the digestive organs simultaneity。Endoscopic ultrasonography has been provenvery effective for diagnosing gastrointestinal diseases.According to the limitation of foreign ultrasonic endoscopes, such as Fujinon’sSP-501 UA, we propose a new design which uses a micro ultrasonic motor situated atthe tip of the endoscope to rotate the transducer. The ultrasonic motor and thetransducer compose a micro probe which enters the coelom through the biopsychannel of the electronic endoscope to get scanning images of the digestive organs. Asa result, the life-span of the ultrasonic endoscope is increased greatly.The main researches of this dissertation are shown as the following:1. According to the structure of the biopsy channel of the endoscope, a microultrasonic probe is presented which is composed of a micro ultrasonic motor and amicro transducer. The external diameter of the probe is 1.8 mm, the inflexible lengthis 14 mm and the scanning frequency is 5 frame per second. In the experiment, theprobe can revolve continually for about a month with a stable revolving speed.2. In order to increase the penetration depth and the image quality of theultrasonic endoscope, a fully digital ultrasonic imaging system is designed which ismainly composed of the following parts:a) Introduce the coded excitation technique which is widely used in radarsystem into the ultrasonic imaging system. The coded excitation techniqueuses a coded pulse to excite the transducer, making the ultrasonic pulsehaving much energy and higher SNR.b) According to the Digital Down Converter technique in software radio, adigital echo receiving system is designed which is composed of a high speedA/D circuit, a digital signal processing circuit (FPGA) and an image savingcircuit. This system places the high speed A/D circuit at the front of the receiving system, sampling the echo at the intermediate frequency. As a result, all the signal processing is implemented by digital circuits which have higher SNR and stability. Moreover, the parameter of the system can be modified with the software easily.c) In order to implement the real-time display of the ultrasonic image, a high speed data transferring circuit is designed which is based on USB2.0 interface.3. Finally, a digital ultrasonic imaging experimental system has been constructed with the designed circuits above. With the experimental system, the coded excitation of the transducer has been implemented. The echo reflected from the glass possesses the character of the Barker code and is consistent with the simulating result in MATLAB. Furthermore a clear scanning image of a glass has been obtained, which validated the performance of the system.更多还原