Magnetic Resonance Imaging at 1.5 Tesla With a Cochlear Implant Magnet in Place: Image Quality and Usability

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Abstract

Objective:

To study the quality and usability of magnetic resonance imaging (MRI) obtained with a cochlear implant magnet in situ.

Study Design:

Retrospective chart review.

Setting:

Tertiary care center.

Patients:

All patients who underwent brain MRI with a cochlear implant magnet in situ from 2007 to 2016.

Intervention(s):

None.

Main Outcome Measure(s):

Grade of view of the ipsilateral internal auditory canal (IAC) and cerebellopontine angle (CPA).

Results:

Inclusion criteria were met by 765 image sequences in 57 MRI brain scans. For the ipsilateral IAC, significant predictors of a grade 1 (normal) view included: absence of fat saturation algorithm (p = 0.001), nonaxial plane of imaging (p = 0.01), and contrast administration (p = 0.001). For the ipsilateral CPA, significant predictors of a grade 1 view included: absence of fat saturation algorithm (p = 0.001), high-resolution images (p = 0.001), and nonaxial plane of imaging (p = 0.001). Overall, coronal T1 high-resolution images produced the highest percentage of grade 1 views (89%). Fat saturation also caused a secondary ring-shaped distortion artifact, which impaired the view of the contralateral CPA 52.7% of the time, and the contralateral IAC 42.8% of the time. MRI scans without any usable (grade 1) sequences had fewer overall sequences (N = 4.3) than scans with at least one usable sequence (N = 7.1, p = 0.001).

Conclusion:

MRI image quality with a cochlear implant magnet in situ depends on several factors, which can be modified to maximize image quality in this unique patient population.

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