Research On Quantification Photoacoustic/Shear Wave Imaging For Early Diagnosis Of Tumors

Due to some factors,the incidence and mortality of global malignancies continue to rise,especially in our country.Worse still,the incidence group is getting much younger.Thus,it is of great practical significance to research into early and nondestructive diagnosis of tumors,which can make an accurate and comprehensive judgment of tumor and provide valid parameter information for further treatment.But the current three evaluation parameters(classification,grading and staging)can only have an effective judgment to a certain degree of tumor,and to obtain these three parameters,the tumor must be sliced,that is detrimental.In order to realize the diagnosis and comprehensive estimation of early tumor,a method to evaluate the tumor based on photoacoustic imaging is presented in this paper.Combining with the scale information,absorption distribution information and elastic information,it can achieve a comprehensive quantitative estimation of tumor development.Firstly,the basic theory of photoacoustic imaging is illustrated,and through the analysis of photoacoustic signal,the tumor size information is obtained.Then k-wave simulation is used to realize the process of setting phantom and obtaining photoacoustic signal.By calculating the obtained photoacoustic signal,the size of phantom is obtained which verifies the accuracy of the calculation method.The development of the tumor can be estimated by its angiogenesis,and the density of the vessels can be reflected by the absorption intensity of the light,that is,the absorption coefficient.The photoacoustic image takes light energy deposition as contrast,and the contrast derives from the absorption coefficient and the local energy flow rate of the tissue,also known as luminous flux.Based on the inherent prior information of absorption coefficient and luminous flux,a quantitative photoacoustic imaging algorithm based on sparse representation is designed to extract the absorption coefficient.The process of light to light energy deposition is realized by Monte Carlo simulation,and the numerical simulation result verified the proposed method.After obtaining the tumor's size and surface development information,the elasticity information is obtained.By comparing the elasticity with the normal mass,we will know whether there is calcification,collagenization or effusion in the tumor.In this part,a shear wave imaging algorithm based on Time-of-Flight algorithm is designed to reconstruct the elastic image through the shear wave displacement data.In order to solve the artifacts in the restored image,a directional filter is designed,and the results show that the filter can successfully filter out artifacts and improve the accuracy of elastic images.Finally,a photoacoustic tomography system is built,and a phantom similar to the tumor model is constructed.The extraction accuracy and feasibility of the scale information,the absorption coefficient distribution and the elastic coefficient are verified by experimenting with the actual photoacoustic signal,photoacoustic image and displacement data.