We have developed a system to simulate a catheter and guidewire in blood vessels for surgical planning, intra-operative assistance and the design of new catheters. The guidewire model is composed of viscoelastic springs and segments. The proximal part of the guidewire model is constrained by the catheter model, which is fixed and assumed to be a rigid tube. The blood vessel model is a circular elastic cylinder, whose shape is defined by the centerline and the radii. Collisions between the guidewire model and the blood vessel model are calculated and the contact forces are determined according to the stiffness of the vessel wall. In our previous study, we evaluated the effects of the parameters of the guidewire and the blood vessel on the simulation system using a torus-shaped vessel model. However, in clinical applications, numerical data should be acquired by image processing of data on the vasculature acquired from the patient. Therefore, in this study, we used patient-specific data and compared the simulation results with medical images for validation of the simulation system. It was shown that guidewire position can be determined using our simulation system.