Magnetic Resonance Imaging at 1.5 T after Pediatric Cochlear Implantation without Magnet Removal

Abstract

Objectives: (1) Assess the safety of 1.5 T magnetic resonance imaging (MRI) in pediatric patients with cochlear implants (CIs) and internal magnets. (2) Assess artifacts created by CI magnets. Methods: A retrospective chart review was performed of pediatric CI patients who underwent 1.5T MRI at a university children’s hospital. Binding of the CI magnet was performed before MRI, using mold material and a compressive gauze dressing. Patients were assessed for ability to complete the MRI, imaging artifact from the CI magnet, magnet position, and CI function following MRI. Results: Four patients (mean age 65 months; range, 19-108 months), and a total of 6 CIs (2 bilateral), underwent 1.5 T MRI scans. There were 3 brain MRI studies and 1 spine. Informed parental consent was obtained. Clinical indications included leukodystrophy (2), hypertonia (1) and dystonia (1). Devices from 2 manufacturers were scanned. A CT scan was performed before the MRI scan in three-fourths of patients to assess bone thickness adjacent to the magnet. Three patients had MRI under anesthesia. The CI produced an artifact with a mean maximal AP dimension of 10.8 mm (range 7.5-15 mm) and a transverse of 5.7 mm (range 5.5-6 mm). Greatest image distortion occurred with bilateral implants. There was no change in magnet position or CI function after the MRI in all cases. Conclusions: Pediatric patients may safely undergo 1.5 T MRI after CI without removal of the magnet if the device is tightly bound beforehand and strict safety protocols are followed. There are limitations to brain imaging due to artifacts.