Endovascular interventions include a variety of techniques, chiefly involving guidewires and catheters, that give access to the vascular system through small incisions. It is imperative to reach the place of interest quickly and safely. By considering the fact that the composition of guidewires and catheters differ (e.g., in material, diameter, length, tip shape, stiffness, and coating), each one shows a different behavior based on its structure, and therefore the choice of instruments becomes challenging. Currently, the choice of the instruments in each procedure is often based solely on a specialist’s experience, which is not sufficient and does not always result in a successful procedure. Therefore, in this thesis, we focus on the performance of the guidewires and catheters with considering their structure.@en

During percutaneous coronary interventions (PCI), a guidewire is used as an initial way of accessing a specific vasculature. There are varieties of guidewires on the market and choosing an appropriate one for each case is critical for a safe and successful intervention. The main objective of this study is to predict the behavior of the guidewire and its performance in a vasculature prior to the procedure. Therefore, we evaluate the effectiveness of different mechanical properties of the guidewire on its behavior. A two-dimensional (2D) model has been developed in which a guidewire is considered as a set of small rigid segments connected to each other by revolute joints. These joints have two degrees-of-freedom to allow rotation. Linear torsional springs and dampers are applied in each joint to account for the elastic properties of the guidewire; the elastic properties have been measured for two commercially available guidewires (Hi-Torque Balance Middleweight Universal II—Abbot and Amplatz Super Stiff—Boston Scientific) and these are used in the model. Only translational motion has been applied to the guidewires and the effect of bending stiffness of the guidewire and also friction between guidewire and vasculature on its behavior are investigated. The results are validated with actual movement of the guidewires in a simple phantom model. Behavior of a guidewire in a vasculature was predicted using the developed model. The results of both simulation and experiment show that the behavior of a guidewire is influenced by its mechanical properties and by the friction between the guidewire and vasculature. This study is the first step to develop a complete model, which can predict the behavior of a guidewire inside the vasculature. We compared the tip trajectory for two commercial guidewires in one vasculature geometry. In future, this kind of knowledge might support not only the interventionist in choosing the best suitable guidewire for a procedure but also the designer to optimize new instrument to have the desired behavior.@en

Guidewires and catheters are used during minimally invasive interventional procedures to traverse in vascular system and access the desired position. Computer models are increasingly being used to predict the behavior of these instruments. This information can be used to choose the right instrument for each case and increase the success rate of the procedure. Moreover, a designer can test the performance of instruments before the manufacturing phase. A precise model of the instrument is also useful for a training simulator. Therefore, to identify the strengths and weaknesses of different approaches used to model guidewires and catheters, a literature review of the existing techniques has been performed. The literature search was carried out in Google Scholar and Web of Science and limited to English for the period 1960 to 2017. For a computer model to be used in practice, it should be sufficiently realistic and, for some applications, real time. Therefore, we compared different modeling techniques with regard to these requirements, and the purposes of these models are reviewed. Important factors that influence the interaction between the instruments and the vascular wall are discussed. Finally, different ways used to evaluate and validate the models are described. We classified the developed models based on their formulation into finite-element method (FEM), mass-spring model (MSM), and rigid multibody links. Despite its numerical stability, FEM requires a very high computational effort. On the other hand, MSM is faster but there is a risk of numerical instability. The rigid multibody links method has a simple structure and is easy to implement. However, as the length of the instrument is increased, the model becomes slower. For the level of realism of the simulation, friction and collision were incorporated as the most influential forces applied to the instrument during the propagation within a vascular system. To evaluate the accuracy, most of the studies compared the simulation results with the outcome of physical experiments on a variety of phantom models, and only a limited number of studies have done face validity. Although a subset of the validated models is considered to be sufficiently accurate for the specific task for which they were developed and, therefore, are already being used in practice, these models are still under an ongoing development for improvement. Realism and computation time are two important requirements in catheter and guidewire modeling; however, the reviewed studies made a trade-off depending on the purpose of their model. Moreover, due to the complexity of the interaction with the vascular system, some assumptions have been made regarding the properties of both instruments and vascular system. Some validation studies have been reported but without a consistent experimental methodology.

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As the connection at the proximal tip plays an important role for sensing guidewires, we compared various sensing guidewires with regard to their proximal connectors. The strengths and weaknesses of each are discussed and recommendations for future development are provided. A literature search limited to the English language for the time period from the 1960s to the 2010s has been performed on the USPTO database, Espacenet, and Web of Science. The results have been categorized on the basis of the connector design. A comprehensive overview and classification of proximal connectors for sensing guidewires used for cardiovascular interventions is presented. The classification is based on both the type of connector (fixed or removable) and the type of connection (physical, wireless, or a combination). Considering the complexity of the currently prototyped and tested connectors, future connector development will necessitate an easy and cost-effective manufacturing process that can ensure safe and robust connections.@en