Visiting Researcher: Hao Liu Article List>> Towards the Utilization of Computational Biomechanics in the Circulatory System 1. Aim and plan of this study This study aimed to provide a platform for an integrative hemodynamic simulator, by which the circulatory function of the human circulatory system could be comprehensively understood, and to which a computational biomechanics system could be applied for clinical diagnosis and pre-operational prediction based on the anatomical and physiological information of the blood circulatory system of an individual patient. The followings are subjects of this study. Subject (1) Medical image processing and vessel modeling: research and development of a method and interface for medical image processing, by which medical procedures, such as vessel extraction, vessel reconstruction, and computational model formation, can be efficiently undertaken Subject (2) Computational program: research and development of a hemodynamic simulator using realistic geometrical and physiological models of an individual patient Subject (3) Application to clinical problems: application to a typical organ in the cardiovascular system (the heart) and arteries with multiple lesion such as a great vessel (the aorta), the carotid artery, the renal artery, and the cerebral artery The computational biomechanics system developed in (1) and (2) was verified by simulations of using this system. Moreover, the possibility and practicability of applying the system to clinical problems, such as the elucidation of the development of arteriosclerosis or an aneurysm and pre-operational prediction, were examined. 2. Abstract of this study (1) Vessel modeling Using high-definition MRI, CT imageing, and X-rays, and supersonic imaging techniques that are popular in medical fields—image digitization, ROI region extraction, vessel reconstruction, and computational grid formation can be routinely processed. (2) Multiscale hemodynamic modeling A multiscale hemodynamic modeling method was developed in which the global circulatory function and local hemodynamics of the cardiovascular system could be evaluated simultaneously. This method consisted of circulatory system network modeling based on a one-dimensional blood vessel model, an image-based three-dimensional blood vessel model with actual shape, and behavior modeling of shearing stress and endothelial cells; the method provided a platform for a cardiovascular system simulator. Using this method, the circulatory function of the whole body can be comprehensively understood. In evaluating the behavior of the entire circulatory system, this method is therefore expected to be applied to clinical diagnosis and pre-operational prediction. Moreover, the influence of newly developed medicines on the circulatory function, including the physiological function of the whole body, will be estimated. (3) Clinical problems Evaluation of the function of the human left ventricle Based on a supersonic image, prototype models of the left ventricle in a normal heart and abnormal heart were created for the computational biomechanics system. By using these models, cardiac function under various physiological conditions could be evaluated. Elucidation of vortex flow in the aorta and the development of an aneurysm Since a computational biomechanics model taking in to account the flow dynamics in a blood vessel could be constructed based on X-ray and supersonic images, the morphology of the vascular system, the three-dimensional shape of a blood vessel, the flow dynamics in a blood vessel, inflow and outflow conditions, and the interaction between shearing stress and endothelial cells could be comprehensively evaluated. The dynamical foundation for the elucidation of the development of an aneurysm was also established. Operational prediction of carotid stenosis Since a computational biomechanics model used for the operational prediction of carotid bifurcation stenosis could be created, the blood flow before and after the operation could be simulated. The result of this simulation was in approximate agreement with actual measurements. Elucidation of hypertension caused by artery stenosis In order to investigate the relationship between the hemodynamics at the bifurcation of the renal artery and hypertension caused by artery stenosis, a computational biomechanics model of the bifurcation of the renal artery was created and the blood flow was simulated. The development of a renal artery bifurcation stenosis will be elucidated in comparison with in vitro experimental data and in vivo measurements. Elucidation of the relationship between the hemodynamics in the basilar artery system and the development of an aneurysm The local circulatory function in the circle of Willis in the basilar artery could be evaluated by using a realistic computational biomechanics model based on an MRI image.