We have developed a computer-based system to simulate a guidewire in blood vessels for surgical planning, intra-operative assistance, and to facilitate the design of new guidewires. In this study, we compared simulation results with experimental results for validation of the simulation system. First, we inserted a commercial guidewire into a poly (vinyl alcohol) hydrogel blood vessel model using a two-axis automatic stage and measured the position of the guidewire tip and the contact force between the guidewire and the vessel. The experimental apparatus can be used not only for the validation of numerical analyses, but also as a simulation system. Second, similarly to the experiment, the motion of the guidewire in the blood vessel model was calculated when the proximal part of the guidewire model was pushed and twisted. The model of the guidewire is constructed with viscoelastic springs and segments, and the proximal part of the guidewire model is constrained by the fixed catheter model. Collisions between the guidewire and the vessel are calculated, and the contact forces are determined according to the stiffness of the vessel wall. The same tendency was seen in the trajectories and the contact force of both the experimental and simulated guidewire tips.

In this study, we propose a force sensor using a shape-memory polymer (SMP) whose stiffness varies according to the temperature. An SMP can be deformed above its glass transition temperature (T _g) by applying a small load. A deformed SMP maintains its shape when cooled below T _g and returns to its predefined shape when subsequently heated above T _g. The reversible change in the elastic modulus between the glassy and rubbery states of an SMP can be on the order of several hundred-fold. The relationship between the applied force and the deformation of the SMP changes depending on the temperature. Our sensor consists of strain gauges bonded to an SMP bending beam and senses the applied force by measuring the strain. Therefore, the force measuring range and the sensitivity can be changed according to the temperature. In this study, we evaluate a prototype of the sensor using the SMP sheet with embedded electrical heating wire. Moreover, we improve the sensor by combining the SMP and a stainless steel plate. The enhanced versatility of SMP force sensors is demonstrated through a series of experiments conducted using the prototype.

To achieve quantitative palpation in vivo, we developed a catheter-type tactile sensor composed of a polyvinylidene fluoride film for minimally invasive surgery. We evaluated the fundamental performance of the prototype sensor by a weight-drop test. We also measured the output of the prototype sensor as it was inserted into a blood vessel model with shapes mimicking lesions. The ø2-mm sensor passed easily into the blood vessel model with lesion-like shapes. Sensor outputs corresponded to the shape of the inner wall of the blood vessel model, making it possible to determine the position of a protrusion and the convexity interval of a rough surface by filtering and frequency analysis of the output.

Tube-shaped blood vessel models that mimic their geometries and mechanical properties can deliver reliable and realistic behavioral information such as deformation and rupture during procedures such as insertion of medical devices. Thickness of vessel walls is an important parameter for fabricating the blood vessel models owing to their strong influence on the model behavior, especially during deformation. The dip-coating method is used to fabricate blood vessel models; however, non-uniform wall thicknesses are observed using this method. This study aimed at finding the characteristics of stereo “angular control dip-coating” (ACDC) system to develop a dip-coating system that can produce tubular models with uniformed wall thickness. The system developed here enables an observation of the substrate behavior from two different views. The conditions of dip-coating used in this study produce 1.36–1.82 mm in the maximum and 0.188–0.435 mm in minimum wall thickness and the fabricated walls cover the realistic range of carotid arterial dimensions. The characteristics of the ACDC system indicate that ACDC is effective for fabricating the uniform wall thickness particularly in the strong curved parts.