A Pneumatic MR-conditional Guidewire Delivery Mechanism with Decoupled Actuations for Endovascular Intervention

Percutaneous coronary intervention (PCI) involves the delivery of a flexible submillimeter guidewire and existing x- ray based approaches impose significant ironing radiation. The use of magnetic resonance imaging (MRI) for intraoperative guidance has the advantages of not only being safe but also having high positioning accuracy and excellent tissue contrast. This paper develops a pneumatically driven MR-conditional delivery mechanism for the ease of manipulation of the guidewire in vivo. It incorporates newly developed rotary pneumatic step motors and a pneumatic slip ring for actuation and decoupling of translational and rotational motions. An effective clamping mechanism for the locking and releasing of the guidewire is also incorporated. The proposed pneumatic slip ring mechanism decouples six gas lines, where four are used to supply a pneumatic step motor for translational motion and two for the clamping mechanism. High friction sil sleeve is used to hold the guidewire firmly. The rotary pneumatic motor has excellent sealing and stability, providing an output torque of 15.75 Nm/MPa. Experiments show that the average error of translational motion is 0.37 mm. Real-time MRI-guided endovascular intervention is performed in a vascular phantom with pulsatile flows to validate its potential clinical use. The imaging artifact test under MRI shows no noticeable distortion and the loss of Signal-to-Noise Ratio (SNR) is less than 2%.