Research Of Signal Receiving System For Medical Ultrasonic Endoscope Imaging

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 quality of the ultrasonic echo is the key factor of the medical ultrasonic endoscope system, so the design of the signal receiving system should consider the depth of penetration as well as the signal-to-noise ratio (SNR).First, the article simply introduces the principle of ultrasonic imaging and the character of EUS. Then according to the application background of digital medical ultrasonic endoscope system, the whole circuit is concretely designed:1. Basing the requirement of the digital medical ultrasonic endoscope system, the framework of the signal receiving system is established, which includes matching circuit, isolating circuit, the amplification circuit, the time gain compensation (TGC) circuit and the band-pass filter (BPF) circuit.2. The whole circuits have been finished. The impedance matching can maximize the signal transmission efficiency, the isolating circuit can isolate the high voltage drive pulse, the amplification circuit with high accurate operational amplifier can offer enough gain to the echo, the TGC circuit can compensate the attenuation while the ultrasonic transmits in the substance, the BPF with improved structure can avoid the self-excitation as well as filter the noise.3. The controlling system based on FPGA is designed to control the timing of the signal transmitting, the timing of signal receiving and the algorithm of the TGC. The function of the system has been emulated successfully and the circuit has been made. 4. All the debug work for both circuits and program are finished. The experiment proves the performance of the whole system, which meets all the requirement of the medical ultrasonic endoscope imaging system.