Original investigationRF Heating of MRI-Assisted Catheter Steering Coils for Interventional MRI
Section snippets
Device construction
A 1.8Fr Baltacci catheter (BALT, Montmorency, France) was obtained, and the most distal catheter tip containing heavy metal marker was cut to eliminate confounding magnetic forces and MR artifacts. A three-axis coil using 44–American wire gauge magnet wire (California Fine Wire, Grover Beach, CA) was wound on the tip of the modified catheter. The z-axis coil was solenoidal and consisted of 100 turns. The two orthogonal modified Helmholtz coils were wound along the side of catheter over the
RF Heating of Handmade Coils in Agarose Gel Phantom
In the absence of applied direct current, experiments were carried out at various distances from the magnet bore wall to determine RF heating effects induced in the solenoid and Helmholtz catheter coils due to RF pulse sequences during real-time MRI. At the isocenter of the magnet, no heating was detected by any of the probes after 15 minutes of imaging (Fig 2a). As the apparatus was moved 5 cm closer to the magnet bore wall, a slight increase in the temperature (0.2°C) recorded over the
Discussion
This study shows that no clinically significant RF-induced heating occurs during real-time SSFP MRI of MR-assisted catheter tip steering for interventional MRI. The maximum increase in temperature observed after 15 minutes of continuous SSFP imaging was 0.35°C at 15 cm from the magnet isocenter, which is well below the 4°C increase that can cause irreversible tissue damage 17, 18. As expected, temperature increases around the coils were directly proportional to the proximity of the
Conclusions
MRI-assisted steering coils for endovascular catheter steering during vascular intervention do not appear to experience significant RF heating. These results, combined with demonstration that resistive heating due to applied direct current can be minimized by transferring heat to saline coolant flowing through catheter lumen, begin to address safety concerns related to the eventual clinical use of this device in vascular interventions and will serve as the basis for further in vivo testing
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This work was supported by grant 5 R01 HL076486-01 to 03 from the National Heart, Lung, and Blood Institute (Bethesda, MD).