**4. Mechanical properties of stent**

It is important to obtain sensitivities of mechanical properties of a stent to design variables when designing the stent suitable for patient's symptom. In this section, important mechanical properties, namely, radial stiffness, flexural rigidity, and shear rigidity, are evaluated and the maps of their sensitivities are made. The expanded stent shape is used for evaluation of mechanical properties. The expanded shape is predicted from the expansion analysis (see in (Yoshino & Inoue, 2010) for details).

Fig. 9. Sensitivities of the mechanical properties of the SENDAI stent 6 mm diameter to thedesign variables: (a) radial stiffness, (b) flexural rigidity, and (c) shear rigidity

This support system has design method of a self-expanding stent suitable for the patient's symptom based on mechanical properties of a stent. This method is available to introduce into the existing design support system described above, and has two stages which are the design and modification methods. In the first stage, a stent shape with mechanical properties suitable for the patient's symptom is determined and designed. In the second stage, to modify the stent shape in consideration of the risk of in-stent restenosis realizes designing the stent shape more suitable for the patient's symptom. The risk of in-stent restenosis is evaluated based on a mechanical stimulus to a vascular wall by insertion of a stent. These two stages of the design

After the two-stage design method, the design support system ends with the generation of the NC data of the designed stent necessary for moving onto the actual production process. For change in a stent shape, a subsystem for generating the two-dimensional shape of the initial stent was introduced, and this is available for changing the two-dimensional shape flexibly. It

It is important to obtain sensitivities of mechanical properties of a stent to design variables when designing the stent suitable for patient's symptom. In this section, important mechanical properties, namely, radial stiffness, flexural rigidity, and shear rigidity, are evaluated and the maps of their sensitivities are made. The expanded stent shape is used for evaluation of mechanical properties. The expanded shape is predicted from the expansion

Fig. 9. Sensitivities of the mechanical properties of the SENDAI stent 6 mm diameter to thedesign variables: (a) radial stiffness, (b) flexural rigidity, and (c) shear rigidity

can also be used to generate a two-dimensional diagram of the stent in the first place.

method will hereinafter be described in more detail (see in Section 6).

**4. Mechanical properties of stent** 

analysis (see in (Yoshino & Inoue, 2010) for details).

We must know the relationship between the mechanical properties of a stent and the design variables in order to design a stent with specific properties. The mechanical properties of the SENDAI stent, such as radial stiffness, flexural rigidity, and shear rigidity, were evaluated, and their sensitivities to the design variables were also defined, as shown in Fig. 9 (Yoshino & Inoue, 2010). The wire length along the axial direction and the wire width were selected as design variables. Isolines on the maps of mechanical properties are very important for proposing designs. The isoline is plotted onto the maps based on the required mechanical property, and design variables of the proposed design are determined from the isoline. In addition, we assumed the mechanical properties of the stent material as illustrated in Fig. 10: Young's modulus of 28 GPa, and Poisson's ratio of 0.3.

Fig. 10. Assumed stress-strain relationship for the stent material
