Ultrasound Beam To Form A Theoretical And Experimental Study

Medical imaging technology plays an important role in clinic. Ultrasound is a useful technology in clinic now as well as X-ray. But ultrasonic image quality is lower than CT and NMRI image, because its beam width is wider than X-ray. And ultrasonic advantage is non-destruction and high ratio between quality and price.But, why ultrasonic image quality is so low? Someone advise that our work would start in the mechanism of ultrasonic oscillation and propagation.Firstly we recall the history of the conventional beam forming. Then introduce the non-diffraction beams. They based on the isotropic (homogeneous) scalar wave equation. A lot of scientists have developed the investigation. In contrast to conventional beams, limited diffraction beams have large depth of field, good focus, but high sidelobes.We obtained a novel kind of limited diffraction beams under Prof. Li's instruction. They are pulse beam and named Nondiffraction Bandlimited Waves (NBWs), and their character is outstanding. They has large depth and non-spreading and bandlimited. To obtain the direct impression, we simulate NBWs from zero-order to 3-order solution. Then we also product the spectra and their ultrasonic field plots.To verify the nondiffraction bandlimited wave, we design the single unit transducer that is mini-probe. When the probe is small enough, we could apply the multi-dot transducer to synthesize the NBWs.Meanwhile our job is focus on the experimental system on the basis of theoretical work. The system consists of two mini-probes which include one is transmitter, another is receptor; the oscillation circuit; the pre-amplifier, and the amplitude-phase detector. Meanwhile we must simulate the data with computer.At last we discuss the beam deforming factor in the experiment; and analyze the limitation and advantage about synthetic method. We also expect the future work of this project.