Design Of Ultrasonic-Probe Driving Control System For Medical Ultrasonic Endoscope

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.