Characterizing Cochlear Implant Magnet-Related MRI Artifact

Area of Science:

• Radiology
• Medical Imaging
• Otolaryngology

Background:

• Cochlear implants (CI) contain magnets that can cause artifacts in MRI scans.
• Evaluating the impact of these artifacts on diagnostic image quality is crucial for patient management.

Purpose of the Study:

• To assess the shape and size of MRI artifacts caused by cochlear implant magnets.
• To evaluate the indications and clinical adequacy of MRI scans in CI patients.
• To compare artifact size across different MRI sequences and identify optimal imaging protocols.

Main Methods:

• Retrospective review of 58 head MRI scans from 20 patients with CIs (2014-2020).
• Recorded scan indications and assessed clinical adequacy.
• Measured magnet-related artifact size using ellipsoid modeling on the slice with greatest signal loss.
• Compared artifact radius across five sequence categories (T1 FSE, T2 FSE, T1 GRE, T2 GRE, DWI).

Main Results:

• Artifact magnitude was significantly greater in T2 GRE (6.86 cm) and DWI (7.56 cm) sequences compared to T1 FSE (4.47 cm).
• T1 FSE, T2 FSE, and T1 GRE sequences showed similar artifact sizes to the reference T1 FSE sequence.
• Clinical interpretability did not significantly differ between scans for known pre-implantation indications versus new issues.

Conclusions:

• Diffusion-weighted imaging (DWI) and T2 gradient echo (GRE) sequences are less useful for MRI evaluation in cochlear implant patients due to larger artifacts.
• T1 FSE, T2 FSE, and T1 GRE sequences are more likely to yield clinically useful information due to a more favorable artifact profile.
• Preoperative optimization for magnet location could improve MRI utility for the substantial number of scans performed for known indications.