Ultrasonic Particle Image Velocimetry In The Evaluation Of Cardiac Function

Cardiovascular diseases that are the world's number one killer of human being,have a very high prevalence,morbidity and mortality.Heart disease is one of the most common cardiovascular diseases.Evaluation of cardiac function contributes to early detection and localization of heart disease in the clinical practice.Currently,existing methods for measuring cardiac function mainly include left ventriculography,blood pool radionuclide ventriculography and echocardiography,which are based on imaging left ventricle morphology and calculate ejection fraction,stroke volume,cardiac output and other parameters through morphological changes to evaluate the cardiac function.Importantly,more and more increasing evidences demonstrate that left ventricular function disorder occur when the heart is impaired,which affects the left ventricular hemodynamic parameters.Thus,left ventricular hemodynamic parameters can be used as a key indicator of cardiac function testing.Currently,methods used to calculate left ventricular hemodynamic parameters mainly include phase contrast magnetic resonance imaging and color Doppler blood flow based on vector flow mapping.Though MR imaging has high three-dimensional spatial resolution,the time resolution is relatively low and the expense is relatively high.Color Doppler ultrasound has the advantages of popular price,time-consuming short and high time resolution,but the method can not accurately measure the velocity perpendicular to the beam direction.Therefore,this paper focuses on ultrasound particle image velocimetry(echo PIV)to measure hemodynamic parameters within the left ventricle,through speed,shear stress,vorticity and other parameters for quantitative evaluation of cardiac function.Our work mainly includes the three aspects,as follows.Firstly,we study the ultrasound particle image velocimetry,in which the cross-correlation was used as the main algorithm.Besides,the sub-pixel algorithm,filtering interpolation algorithm,error vector detection and culling algorithms and iterative algorithms was used to improve the accuracy of calculation.We also characterize hemodynamic parameters that are involved in evaluating cardiac function.Secondly,we study the method of making the left ventricle phantom,and also create different hardness phantoms.Set up experimental system and use ultrasound contrast imaging to image experimental phantoms.Then we use such image data to calculate and statistically analyze the hemodynamic parameters of different hard phantoms.At last we concluded that the larger hardness phantom has much greater value in view of speed,shear force and vorticity than the smaller hardness phantoms.