Research On Significant Techniques In Digital Color Flow Mapping System

As a non-invasive detecting method, color flow mapping (CFM), which can visualize the velocity profile over a large region in real-time, combined with tissue imaging and Doppler spectrum detection, has been among the advanced ultrasound diagnostic devices. Compared to conventional analog system, digital CFM system is more stable, flexible, with more powerful processing ability, has become the mainstream of CFM systems at present.In this thesis, the purpose of the research was introduced in the beginning, and the recent development of CFM technology was reviewed. Then, the basic principle of CFM was analyzed and some fundamental knowledge of signal processing was introduced. Radio frequency (RF) pulse echo signals containing flow information were calculated using Field II. Thorough research on algorithms of primary signal processing chains was carried out by simulation. Conclusions drawn from the simulation were validated by processing the pulse echoes data from a series of experiments.Combining the results from both simulation and experiments, narrow-band (phase domain) system is superior to wide-band (time domain) system in estimating precision, sensitivity, robustness to noise, and less computational complexity, except the velocity-range barrier and axial resolution. Thus it is the first choice of mini digital CFM system designing scheme. Furthermore, schemes or algorithms on transmitting pulse, echo signal demodulation, clutter rejection, velocity estimation and threshold setting were discussed, providing valuable reference on design as well as implementation of CFM system.