Application Of Hydrophone Array In Shock Wave Echo-Positioning

Since 1980,ESWL(Extra-corporeal Shock Wave Lithotripter)have relieved patients all over the world from sufferings brought by kidney and urinal calculus.But one major problem about lithotripter is the accuracy of targeting,a proportion of shock waves miss the stone,which result in reduced therapeutic effect,complications and reoperation.Positioning technologies in use bear various theoretical defects,it has practical significance bringing out a reliable and easy-to-implement way of targeting stone during lithotripsy,and the technic will improve the efficiency of this operation.Upon elaborating the significance of this work,research status quo is introduced,relevant knowledges regarding general acoustics and shock wave are also introduced.After that,positioning effect of shock wave is discussed,formula derivation describing sound wave scatter from a rigid sphere is presented,and along with it the directivity diagram under certain "kr" values,which leads to the conclusion that it is viable to locate the stone by analyzing scatter signal.Afterwards there is a brief introduction to different types of echolocation algorithms,and a detailed one on trilateration.Water tank experiment system is built,including water tank frame and box,motion mechanism,control box,DAQ device and other apparatuses used in experiments.LabVIEW software and PLC software are written to meet the needs of experiments.A number of technical problems are solved building the system."circular hydrophone receiving performance experiment" and "hydrophone array shock wave scatter signal receiving experiment" are designed and conducted.In the first experiment,it is proven that circular array is capable of receiving scatter signal.In the second experiment,feasibility of shock wave echo-positioning is confirmed through identifying scatter waveform characteristic of the stone.Trilateration is applied to experiment data,yielding the positioning error less than 2mm on X-Z plain.In the last part of this dissertation,positioning error,valid range and accuracy of the technic is discussed,achievement of this work is summarized,a few deficiencies are pointed out,future development and application prospect of this technic are briefly discussed.