Author + information
- 1National Key Laboratory of Complex System Intelligent Control and Decision, School of Automation, Beijing Institute of Technology, Beijing, P.R
- 2Department of Cardiology Internal Medicine, Nanlou Branch of Chinese PLA General Hospital, Beijing, P.R.China
- 3Mathematical Institute, University of Oxford, Andrew Wiles Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford, UK
Myocardial infarction caused by cardiovascular blockage often shows local myocardial motion state change, thus it is helpful that a patient-specific finite element model of the heart is reconstructed.
This article presents several steps to reconstruct cardiac model and do some finite element based analysis. In the first step, CT scan of a patient diagnosed with myocardial infarction was used, and the cardiac tomographic images of different period, respectively 20%, 40%, 60%, 80% and 100% were obtained. In the next image segmentation process, a new parameter active contour model based on automatic initialization, and mixture of the balloon force and gradient vector flow was proposed. The automatic initialized curve deformed under inner and outer energy, balloon force and gradient vector flow, soon would make the motion curve meet the target boundary. The data of each cycle was saved as DICOM format and imported into Mimics 17.0. After that, Mimics was used to do three-dimensional reconstruction, and the results were exported as IGES format. Secondly, NURBS was generated and modified. The grid dimension was set to 512×512×432, and X-Y-Z-axis step length was set to 0.390625, 0.390625, 0.3 mm. Then, the shape of NURBS was adjusted. At last, the finite element models of each period after treatment were imported into Ansys 17.0 to do analysis.
A detailed three-dimensional nonlinear cardiac finite element model of a whole systolic and diastolic cycle was obtained, which allowed doctors and other medical personnel to observe both the static and the dynamic heart model directly. Based on the heart muscular fiber arrangement, a unique biological material library of Poisson's ratio and modulus of elasticity of different parts of the heart was established. In each period and at each part of the heart, the model was defined with certain different coefficients. The processing and analysis of the finite element model of a whole cardiac cycle provide cardiac function parameters such as left ventricular volume, ejection fraction and cardiac output. Patient cardiac parameters were compared with normal indicators, and the results were shown effective enough. Cardiac range of motion and myocardial amplitude, velocity and acceleration of the model can be used to track the lesion to assist medical treatment.
Improved contour model expanded the boundaries of the curve searching range, and gave a better solution to the division of the depth of the recessed area. By using the created biochemical material library to do analysis, more accurate results were gotten compared with the conventional average material rigidity definition.