MRI Conditional Actively Tracked Metallic Electrophysiology Catheters and Guidewires With Miniature Tethered Radio-Frequency Traps: Theory, Design, and Validation

• Published in: IEEE transactions on biomedical engineering Vol. 67; no. 6; pp. 1616 - 1627
• Main Authors: Alipour, Akbar, Meyer, Eric S., Dumoulin, Charles L., Watkins, Ronald D., Elahi, Hassan, Loew, Wolfgang, Schweitzer, Jeffrey, Olson, Gregory, Chen, Yue, Tao, Susumu, Guttman, Michael, Kolandaivelu, Aravindan, Halperin, Henry R., Schmidt, Ehud J.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01-06-2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Ablation; active tracking; Attenuation; Baluns; Braiding; Cables; Catheters; Design; Electromagnetic coupling; Electrophysiology; Inductive coupling; Livestock; Magnetic fields; Magnetic resonance imaging; Mechanical properties; MRI intervention; Navigation; Optimization; Radio frequency; resonance RF traps; RF safety; Solenoids; Standing waves; Swine; Visibility; Wires
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2019.2941460

Objective: Cardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns). Method: MBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine. Results: Electromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ~17 dB/MBalun surfacecurrent attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility. Conclusion: MBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI. Significance: MBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.