Device visualization for interventional MRI using local magnetic fields: basic theory and its application to catheter...

Area of Science:

• Medical Imaging
• Biophysics

Background:

• Interventional magnetic resonance imaging (MRI) faces challenges in visualizing medical devices.
• Locally induced magnetic fields from devices disrupt MRI's main magnetic field homogeneity.
• This disruption causes signal loss and phase image disturbances, hindering device tracking.

Purpose of the Study:

• To present a method for visualizing interventional devices, specifically catheters, during MRI procedures.
• To theoretically and computationally analyze the impact of induced magnetic fields on MRI signal and phase.
• To validate the proposed visualization technique using simulated and experimental data.

Main Methods:

• A method using a closed copper loop with low current to induce local magnetic fields along the device.
• Simulations to assess intravoxel dephasing effects, excluding susceptibility and RF artifacts.
• Verification of theoretical models with scanned and simulated MRI data.
• Discussion of various wire loop configurations and proposal of two catheter visualization scan types.

Main Results:

• Simulations quantified intravoxel dephasing effects caused by the induced fields.
• Scanned and simulated data confirmed the theoretical predictions regarding signal and phase disturbances.
• Evaluation of different wire loop designs for optimal catheter visualization.
• Successful demonstration of the technique in a pig study for intravascular interventions.

Conclusions:

• The proposed method effectively visualizes catheters during MRI-guided interventions.
• This technique shows significant promise for improving the safety and efficacy of intravascular procedures under MRI guidance.
• Further development could enhance real-time device tracking in interventional MRI.