Application Of Finite-Different Time-Domain Method In Limited-Diffraction Ultrasonic Field

In bio medical ultrasound imaging, acoustic field computer simulation is an important research means, mam researchers pay close attention to it.The useage of sound field simulation to study the ultrasound imaging has good repeatability, high precision, flexibility, efficiency and with low cost, these advantages are obvious in practical use.This thesis concentrates on the finite difference time domain algorithm in plane rectangular coordinates and cylindrical coordinates of the ultrasonic field and the application of ultrasonic non diffraction wave field simulation. We got the following several aspects of research results:1. This thesis studies the finite difference time domain algorithm in plane rectangular coordinates and cylindrical coordinates in ultrasonic field; it gives a specific spatial diseretization method, theoretical derivation and recursive formula.2.In this thesis, the boundaries of ultrasound field in plane rectangular coordinates and cylindrical coordinates are calculated with second order Mur absorbing boundary condition, some individual points of the ultrasound field are calculated in a special way, and finally the FDTD algorithm is successfully used in ultrasonic non diffraction wave sound field simulation, the results are satisfactory.3.This thesis proposed one simplified method which is based on the axis symmetry properties of non diffraction wave to make a nondiffraction field, the method uses a set of concentric annular ultrasonic transducers to obtain an approximation of non diffraction wave source.The simplified generation method has the advantage of simple structure.This research is sponsored by "Research of Imaging Method with Bone Mineral Density Measurement BUA Parameter Based on Non-diffraction Beam"(No.60871087) of NSFC (National Science Foundation of China).