Magnetic resonance imaging compatibility testing of the Clarion 1.2 cochlear implant.

OBJECTIVE

This study aimed to investigate the compatibility of the Clarion 1.2 magnet-containing cochlear implant with a 1.5-tesla (T) and 0.3-T magnetic resonance imager.

BACKGROUND

Cochlear implants restore functional hearing to patients with sensorineural deafness. With the rapidly increasing number of patients with cochlear implants, there is a need to investigate the implant's magnetic resonance imaging (MRI) compatibility.

METHODS

The authors tested the potential torque and force on the metallic components of the implant, heating of the implant and surrounding tissue, unintentional output, implant damage, and image distortion. Tests were performed in both a 1.5-T and 0.3-T MRI.

RESULTS

The torque experienced by the implant in the 1.5-T MRI (0.19 nm) was large enough that it could potentially cause implant movement in some patients. An acceptable amount of torque (0.04 nm) was found in the 0.3-T MRI. Image distortion occurred in the area directly around the implant with a radius of up to 60 mm in the 1.5-T MRI and 100 mm in the 0.3-T MRI. In both MRI units, there was no detectable temperature increase or unintentional output. There was no implant damage except that with worst-case conditions, the internal magnet was demagnetized by 78.5% with the 1.5-T unit and 3.36% with the 0.3-T unit.

CONCLUSIONS

The authors recommend patients with cochlear implants avoid imaging in a 1.5-T MRI. The results suggest that the 0.3-T MRI poses little or no risks to patients with cochlear implants.