We started Computational Biomechanics Research project at RIKEN in 1999. This project includes circulatory simulation, soft and hard tissue simulation and human motion analysis. In the circulatory simulation, we have developed several simulation codes, such as, a fluid - structure coupling simulation code, blood flow simulation codes for the left ventricle and the aorta, kidney artery, carotid artery and stenosis in the brain. In addition, we have also developed both image processing code to handle medical images to get the shape of the artery and mesh generation code for simulation. Using these codes, we can estimate the effects of surgical operation such as removing stenosis or the stent, etc. Parallel conputation is usually used to increase computation speed of one simulation but it should be used to combine one compornent with others to simulate whole human body in biomechanical simulation.

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The paper aims to investigate the relationship between cerebrovascular morphology and hemodynmaics in order to predict rupture and creation of cerebral aneurysms. The authors have been developing an image-based simulation system together with a database system. Using 19 cases of the middle cerebral artery (MCA) analysis from the database system, the multiple regression analysis is performed to estimate a maximum value of wall shear stress. The results are compared and show good agreement with those of numerical analyses.

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There are two kinds of in silico organ which means an organ model in a computer (in silicon tips). One is constructed with mathematical principles, which should be called a virtual organ, and the other is reconstructed by 3D image data, which should be called a virtualized organ. Both are complementarily necessary, and clinically useful simulation will be realized by fusing virtuality of the virtual model and reality of the virtualized organ. The present author has named the goal of organ modeling “real virtuality”. The present paper shows virtual breathing lung which contains anatomical structures and functional behavior in 4D space. In addition, preliminary trials towards the real virtuality are demonstrated.

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Recently, digital system of clinical record is widely used for the convenience of hospital management. Whereas, in terms of the digital record of diagnosis, therapy, and surgery, the interface to input clinical operations is not enough on simpleness and swiftness. To manage and analyze surgical information totally, we have been developing a total computer management system of surgical information which includes quantifications of pre-/post-diagnosis and surgery and a framework of surgical reporting. In this paper, we show results of our researches and its effectiveness.

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Diffusion of the water molecule in the brain is restricted by the white matter fibers. Tensor analysis of the proper diffusion-weighted data set provides quantitative analysis of the white matter diffusion anisotropy as well as fiber tracking (tractography) of the white matter. Preliminary clinical experience of diffusion tensor tractography was assessed.

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Palpation has no standard education system and effective methods of training in internal medicine and surgical procedures. This paper proposes an advanced and integrated VR simulation framework supporting palpationthat makes importance of face sensation. The framework enables palpation of a beating aorta in cardiovascular surgery and indirect palpation for breast and prostatic cancer. Applying blood pressure to inner wall represents beat and enables users pinch beating organs. Interaction model between elastic objects simulates collisions of multiple organs and enables indirect palpation, in which doctors palpate the tissue of interest by touching interposing tissue. The system supports pre-processing procedures, in which elasticity and physical constraints of virtual organs are set for subsequent physics-based simulation, as well as real-time simulation procedures. Since palpation requires high resolution of haptic feedback, deformation and reaction forces are calculated based on finite element methods with several optimization methods. Users can palpate virtual organs with haptic devices and perceive stiffness of tissue. The evaluation with medical experts and students confirmed the developed system be useful for the experience, education and training of many kinds of palpation diagnosis.

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Virtual endoscopy in CT is a function in which internal structures of the human body can be observed interactively while moving the viewpoint. This function is realized by image processing of the 3-dimensional volume data. It also allows structures that cannot be observed using a real endoscope to be examined with low invasiveness. The Toshiba X-ray CT system Aquilion Super Heart Edition supports scanning of 16 slices in 0.4 second as well as the virtual endoscopy function as a clinical application. This paper describes the techniques employed in virtual endoscopy and also discusses other applications that are related to this technique.

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