Magnetic Resonance Imaging at 1.5 Tesla With a Cochlear Implant Magnet in Place: Image Quality and Usability.
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.
Sharon, JD; Northcutt, BG; Aygun, N; Francis, HW
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