Active delivery cable tuned to device deployment state: Enhanced visibility of nitinol occluders during preclinical interventional MRI

Purpose: To develop an active delivery system that enhances visualization of nitinol cardiac occluder devices during deployment under real-time magnetic resonance imaging (MRI). Materials and Methods: We constructed an active delivery cable incorporating a loopless antenna and a custom titanium microscrew to secure the occluder devices. The delivery cable was tuned and matched to 50Ω at 64 MHz with the occluder device attached. We used real-time balanced steady state free precession in a wide-bore 1.5T scanner. Device-related images were reconstructed separately and combined with surface-coil images. The delivery cable was tested in vitro in a phantom and in vivo in swine using a variety of nitinol cardiac occluder devices. Results: In vitro, the active delivery cable provided little signal when the occluder device was detached and maximal signal with the device attached. In vivo, signal from the active delivery cable enabled clear visualization of occluder device during positioning and deployment. Device release resulted in decreased signal from the active cable. Postmortem examination confirmed proper device placement. Conclusion: The active delivery cable enhanced the MRI depiction of nitinol cardiac occluder devices during positioning and deployment, both in conventional and novel applications. We expect enhanced visibility to contribute to the effectiveness and safety of new and emerging MRI-guided treatments.