Magnetic resonance imaging safety-driven, heat-mitigating design for a magnetic resonance imaging-guided, magnetically actuated robotic catheter.

BACKGROUND

Metallic components in magnetic resonance imaging (MRI)-guided robotic catheters, such as leadwires and microcoils, can interact with the scanner's radiofrequency (RF) fields, causing heating via the antenna effect and Joule heating, leading to localized temperature rises and an increased risk of thermal injury. Ensuring thermal safety will enable safe and reliable operation of magnetically actuated robotic catheters within MRI environments.

PURPOSE: This study aims to develop a novel MRI-compatible robotic catheter design that mitigates RF-induced and resistive heating, ensuring patient safety and proper functionality during MRI-guided interventions, particularly for cardiac ablation procedures. The catheter is directly actuated by magnetic torques generated on current-carrying microcoils at the tip by the MRI scanner's static magnetic field, allowing precise navigation.

METHODS

The catheter design incorporates systematically tuned microcoil parameters and distributed capacitors along the leadwires to suppress resonance and minimize RF energy absorption. A dithering technique applying actuation currents at a 50 % duty cycle (10 Hz, 50 ms on/off) promotes forced convection to reduce resistive heating. A resistor-capacitor (RC) equivalent circuit model was used to characterize the catheter's thermal behavior. Thermal validation was conducted on a 3T MRI scanner using a saline-filled phantom, fiber-optic temperature probes, and a balanced steady-state free precession (bSSFP) imaging sequence with actuation currents up to 1 A. Hot spot detection sweeps along the leadwires and spatial heating assessments at multiple bore positions were also performed.

RESULTS

The prototype exhibited a maximum temperature increase of 0.6 ∘ C during simultaneous imaging and 1 A dithered actuation, well within Food and Drug Administration (FDA) safety limits. No hot spots were detected along the leadwires, and thermal performance remained consistent across all bore positions tested.

CONCLUSIONS

The catheter design effectively mitigates both RF-induced and resistive heating under the tested conditions. These results demonstrate the suitability of the design for MRI-guided interventional procedures under the tested conditions, while remaining within FDA temperature limits.