Reconstruction Of Cardiac Dynamic Model And Analysis Of Stress Strain

Because the impetus of heart came mainly from the left ventricle, mechanical analysis ofthe heart is mostly concentrated on the left ventricle. It becomes a research hot spot toreconstruct three-dimensional left ventricle mechanical model by dynamic time-varying medicalimage and use the model to analyze the motions and functions of left ventricle, in which thestrain and stress analysis can reflect the regional function of left ventricular and realize earlydiagnosis and treatment of disease, so the research has become particularly important.The existing ultrasound image based two-dimensional circle strain and strain rateparameters can be used to describe the cardiac twist, but they can not be used to accuratelyreconstruct the three-dimensional twist of heart. This paper started the research ofthree-dimensional calculation method of left ventricular shear strain and stress, and provided atheoretical basis for the subsequent three-dimensional analysis of cardiac twist. Meanwhile, forthe analysis of left ventricular radial and axial movement, it is necessary to model the overall leftventricle. For traditional finite element method can not be directly used on the CAD model (suchas the B-spline, NURBS) to do a mechanics analysis which has continuous distribution in space,this paper uses B-spline solid modeling to construct a continuous left ventricular mechanicalmodel and introduces isogeometrical analysis to calculate stress and strain of the left ventriclewith continuous distribution.Works and contributions of this paper are as follows:1. With the discussion and analysis of cardiac images and the characteristics of heartfunction parameters, finite element modeling and B-spline solid modeling was respectively usedto construct left ventricular mechanical model, which provided the model basis for thesubsequent mechanical analysis.2. The two-dimensional circumferential strain and strain rate that can not be a goodresponse to the three-dimensional case, so triangular mesh surface model was constructed andthe plane finite element was implemented for calculations of tangent left ventricularthree-dimensional strain and stress. Experiments show that this method can not only effectivelycalculate tangent stress and strain of left ventricle, but the visualization results can also directly reflect the status of its three-dimensional twist.3. With the situation that traditional finite element method can not be directly used on theCAD model to do a mechanics analysis which has continuous distribution in space, this paperuses B-spline solid modeling method to establish a continuous left ventricular mechanical modeland with the introduction of other geometric analysis, derived stress-strain calculative formulasare given. Compare with the traditional finite element models, this model is characterized bycontinuous, smooth and inseparable. Meanwhile, the paper establishes cylindrical coordinatesternary B-spline model of the left ventricle which is more approximate the original data.4. According to different times of the left ventricular hexahedral finite element model andB-spline solid model, displacement information of left ventricular is obtained, and strain-stresswere calculated with corresponding visual results. Experimental results show that stress andstrain distribution of the left ventricle can be given by both of them, but by comparing the resultsof them, it is shown that the latter one can give smooth and continuous calculation of leftventricular stress and strain, which can more truly reflect the left ventricular stress and straindistribution, so it is better than the former one.