Evaluation of unintended electrical stimulation from MR gradient fields.

Area of Science:

• Biomedical Engineering
• Medical Imaging Physics
• Computational Electromagnetics

Background:

• Patients with active implants (e.g., cardiac pacemakers, neurostimulators) face safety risks during MRI due to magnetic gradient fields.
• Induced electric fields and currents along implant leads, particularly at the distal tip, can cause unintended stimulation.
• Previous experimental evaluations of these induced fields have been conducted.

Purpose of the Study:

• To computationally evaluate the electric fields induced in active implant leads during MRI.
• To compare computational results with existing experimental data.
• To assess the influence of computational parameters and experimental probe design on results.

Main Methods:

• Utilized two commercial software packages, SemcadX and COMSOL Multiphysics, for computational modeling.
• Analyzed electric field values within 1-3 mm of the implant lead's distal tip.
• Investigated the impact of the two-electrode experimental probe and computational mesh resolution on the results.

Main Results:

• Computational results showed reasonable agreement with prior experimental data at distances greater than 2-3 mm from the lead tip.
• Significant variations (up to one order of magnitude) were observed based on computational mesh size (0.1 mm for SemcadX vs. 0.5 mm for COMSOL).
• The dimensions of the two-electrode probe notably affected the computed electric field values.

Conclusions:

• Computational methods can effectively evaluate induced electric fields in active implants during MRI.
• Careful consideration of computational mesh resolution and experimental probe dimensions is crucial for accurate safety assessments.
• Findings highlight the need for precise parameter selection in both simulation and experimental studies for reliable MRI safety evaluations.