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Synthetic Aperture Ultrasound Image Compression Based On Sparse Represebtation

Posted on:2019-02-09Degree:MasterType:Thesis
Country:ChinaCandidate:W H PeiFull Text:PDF
GTID:2348330563954694Subject:Physics
Abstract/Summary:PDF Full Text Request
Ultrasound imaging non-destructive testing technique can not only detect whether the defects existing in the target material,but also quantify the approximate size and position of the target defect,which is more conducive to the determination of defects.In order to obtain high-resolution ultrasound images,non-destructive testing researchers have applied the principle of synthetic aperture radar to ultrasound imaging,namely,ultrasonic synthetic aperture focusing(SAFT).Ultrasound synthetic aperture focusing technique which improves the image quality to a certain extent.However,the data volume is too enormous,which leads to the complexity of subsequent algorithms.In this thesis,a sparse compression method based on improved MP algorithm is researched.Under the condition that the image is not obviously distorted,the ultrasonic echo signal is compressed and quantized,which improves the storage and transmission efficiency of the system.This thesis first studies the basic principles of signal sparse representation and several sparse decomposition algorithms that are commonly used at the present stage.Firstly,the characteristics of ultrasonic echo signals are analyzed,Gabor overcomplete atom dictionary is built.According to the prior information of the time-frequency parameters of ultrasonic echoes to reduce the computational complexity by simplifying the Gabor overcomplete atom dictionary without destroying the redundancy of it.In the meanwhile,an improved MP algorithm is used for sparsely decomposing ultrasonic echo signals,which solves the problem of large data volume in ultrasonic synthetic aperture technology to a certain extent.Finally,through simulated single-point defects,multi-point defects at different depths,and complex cysts,the ultrasonic echoes received by each probe are compressed with different compression ratios using a sparse compression method based on improved MP.Then send the ultrasonic echoes to the ultrasound imaging system for final imaging.As is shown in result figures that the reconstructed image is basically the same as the original image,the contrast is nearly no difference with the original image.At the same time the better recovery effect is got.After quantitative analysis and lateral resolution analysis of the error,it can be seen that only a few atoms are used for reconstructing the ultrasonic echo signal.The error in the figure mainly comes from the high-frequency part of the signal,andthe envelope part can be accurately recovered.Lateral resolution The rate is basically the same as the original image.The experimental results show that the MP-based sparse compression method can effectively compress the ultrasonic echo signal under the premise of guaranteeing the imaging quality,reduce the system storage and improve the system transmission efficiency.This thesis provide a new solution to solve the problem of large amount of data in ultrasonic synthetic aperture focusing imaging technique.
Keywords/Search Tags:ultrasonic synthetic aperture, Gabor atom library, sparse decomposition, signal compression
PDF Full Text Request
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