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Stent placement is a minimally invasive procedure that has received considerable attention as a treatment option for vascular stenotic lesions associated with coronary atherosclerosis. However, the severe problem of in-stent restenosis has recently begun to occur in blood vessels in which long-term placement of stents has occurred. In-stent restenosis results from the increase in neointimal hyperplasia caused by the stimulus of the force on the vascular wall. In the present study, methods are proposed to compute the contact force and straightening force on a vascular wall. The force on the vascular wall is calculated using these methods. As an example, the force on the vascular wall created by the insertion of the stent into the carotid artery is calculated, and the concentration of the force at both ends of the stent is confirmed. Guidelines are presented to modify the stent shape based in order to remove this force concentration which may provoke the neointimal hyperplasia. The methods described in the present paper are easily applied to the shape design of stents and will be an effective tool for improving the stent shape. [ABSTRACT FROM AUTHOR]

A medical device of mesh-shaped tubular structure, called a stent, is frequently used to expand the stenosis of a blood vessel. The stent normally has the structure of longitudinally repeated wavy wire parts and strut parts, and its mechanical properties, such as bending flexibility and rigidity in the radial direction, mainly depend on the shape of the wavy wire and the construction of the strut. This paper presents, a design support system for self-expanding stents that can design stent shape and evaluate stent performance as routine flow. A two-stage method for designing suitable stent shapes is built into this system. The mechanical properties of self-expandable stents are evaluated using a non-linear finite element method. The wire length of the stent and the wire width are adopted as design parameters, and the sensitivity of the mechanical properties to these parameters is obtained. When the patient's conditions, such as blood vessel type and the diameter of the blood vessel with stenosis, are given by medical examination, the performance of the stent in restoring blood flow has to be determined. Finally, a method is proposed for designing suitable stents with the desired performance on the basis of mechanical properties. [ABSTRACT FROM AUTHOR]

We perform the Monte Carlo simulation of the spiral galaxy formation by using a model which includes the effect of shockwave of supernova explosion in the stochastic process for the star formation. We analyze the fractal dimension of the spiral galaxy obtained by the two-point correlation function method. The calculated fractal dimensions are discussed in comparison with those of the present universe and the early universe. In our simulation, the fractal dimension is obtained as D ≈ 1.3, which is close to the value of the present universe. [ABSTRACT FROM AUTHOR]