Research On Probe Design And Real-time Digital Scanning Converter For Medical Endoscopic Ultrasound Imaging

To diagnose disease of the alimentary canal, changes of mucous membrane suffice fail to provide sufficient information to make out an objective diagnosis of the pathological changes. However, Endoscopic Ultrasonography System (EUS) can help obtain clear and accurate ultrasonic tomography images, and thus provide objective and sufficient information for diagnosis and therapy; In addition, compared to other imaging methods, the ultrasonic imaging are non-invasive, free of ionization and radiation, good at repeatability. The procedures to develop the EUS include probe design, image acquisition and image pre-processing. Due to limited size of biopsy channel, the probe design is confronted with many difficulties, esp. micro-motor and high frequency micro-transducer; In the B-mode sector scan ultrasonic imaging system, the raw image is in polar coordinates, therefore, it is main tasks of image pre-processing to achieve image coordinate transform and interpolation. Through introducing the advanced micro-ultrasonic motor and the front motor design into mini-probe design, an EMI free, steady, long life motor with large torque is obtained; the Piezo-composite and single element spherical transducer are employed to achieve the high bandwidth, high sensitivity of the EUS probe.The CORDIC algorithm is adapted to convert the polar coordinate image to the rectangular coordinate image, while cubic spline interpolation is used to interpolate the vacant pixels. To achieve the real-time feature, the spatial computation ability of FPGA is fully explored to enhance the parallel, pipelined computing. Based on FPGA and Verilog HDL, the proposed algorithms are complied and verified. Simulation results performed in Matlab and Quartus II environments prove that the proposed algorithms can achieve satisfying image quality and real-time feature.This system uses ultrasonic video with image size of 512×512 and frame frequency of 15Hz. The time delay between image input and output is a frame cycle or around 67ms, so that human eyes hardly can perceive the delay and consequently it is a real-time process. It is proved by error source analysis and image processing accuracy analysis that the proposed algorithms have a satisfying accuracy. In the end, features of the whole system are summarized and further work for improvement is indicated.