Cochlear implant with a non-removable magnet: preliminary research at 3-T MRI

Area of Science:

• Biomedical Engineering
• Medical Physics
• Otolaryngology

Background:

• Cochlear implants are crucial for hearing restoration.
• Magnetic Resonance Imaging (MRI) is a vital diagnostic tool.
• Compatibility between medical devices and MRI is essential for patient safety.

Purpose of the Study:

• To evaluate the 3-Tesla (3T) MRI compatibility of cochlear implants with non-removable magnets.
• To assess potential risks such as temperature changes, electronic malfunction, and magnet demagnetization.
• To determine the influence of magnetic field orientation on implant performance.

Main Methods:

• In vitro testing of six cochlear implants for thermal and electronic integrity.
• Measurement of internal magnet demagnetization across 65 implants at varying tilt angles (bi/b0).
• In vivo testing with 28 volunteers assessing implant function in different head positions during MRI.

Main Results:

• No significant temperature increases or electronic malfunctions were observed in vitro.
• Considerable magnet demagnetization occurred, influenced by the angle between the implant's magnetic field (bi) and the MRI's main magnetic field (b0).
• Demagnetization risk was minimal (<6.6%) when the bi/b0 angle was near 90°, but increased significantly (>90°), affecting nearly 60% of cases.

Conclusions:

• Cochlear implants with non-removable magnets remain contraindicated for 3T MRI.
• Magnet demagnetization is directly correlated with the bi/b0 angle and head positioning within the MRI.
• Further research into potential future solutions for MRI compatibility is warranted.