Research On The Forward And Inverse Methods In Uitrasound CT System

Currently, ultrasound imaging technology has played a pivotal role in many field. Such as the industrial detection of flaw and the medical imaging. However, current commercial ultrasound systems use simplifying approximations. So the resolution is far below the theoretical resolution. By contrast, ultrasound CT imaging can be quantitatively and truly restored the speed of sound and attenuation coefficient of acoustic characteristics inside the object. But the algorithm of ultrasound CT imaging may contain large-scale inverse problem and ill-posedness; so, how to put forward and build a comprehensive and practical ultrasound imaging system is vital important and difficult.This paper is on the basis of our earlier research. And we propose a method to achieve sub-wavelength resolution through nonlinear inversion.Firstly, this paper reviews the research background, the research status, the development process and the general method of ultrasound CT imaging. After that, this paper makes a more detailed description and analysis about the wave equation. Finally, a basic model for the forward and inverse imaging algorithm with its integral equation is given.Secondly, this paper makes a more detailed research about the forward imaging algorithm. We introduce a novel preconditioner, together with stabilized biconjugate-gradient FFT method, externed Born method to solve forward imaging problems. And it greatly compresses computation time at the same accuracy condition. As for the inverse imaging part, we introduce the extended contrast source algorithm. Through this approach, we can get a reasonable solution without the ill-posedness problems. Besides, the iteration process doesn’t need the results from the forward imaging part. This process can greatly reduce the number of calculations and reduce the amount of data needed to be processed, and then the algorithm can be robust and faster. Finally, the combination of the forward and inverse imaging algorithm into a complete set of ultrasound CT imaging system. And through some examples to test, the system can achieve super-resolution imaging. Besides, it also can achieve very good results for medical imaging.