The usefulness of the O-MAR algorithm in MRI skull base assessment to manage cochlear implant-related artifacts.

Objective: To assess artifact size and MRI visibility when applying the "Orthopedic-Metal Artifact Reduction" (O-MAR) algorithm for cochlear implant (CI) scanning. Methods: Two volunteers were submitted to 1.5 T MRI with an Ultra 3D CI receiver stimulator placed on their head. Four angular CI orientations were adopted: 90, 120, 135 and 160 degrees. Volunteers were scanned in each condition using T1w and T2w TSE sequences, as well as O-MAR sequences, in both axial and coronal planes. Quantitative comparisons were made of signal void and penumbra extent. Additionally, qualitative evaluations of global image quality, MRI readability with respect to 12 anatomical structures and visibility through the penumbra were undertaken. Results: After application of the O-MAR protocol, the radius of the signal void reduced from 50.76 mm to 45.43 mm and from 49.22 mm to 40.15 mm on T1w and T2w TSE axial sequences, respectively (p < 0.05). Qualitatively, sequences acquired with O-MAR produced better outcomes in terms of image quality and anatomical depiction. Despite the area of the penumbra being increased for the O-MAR protocol, visibility through penumbra was improved. Conclusions: Application of O-MAR may provide a complementary strategy to those already in use to obtain diagnostically useful MRI examinations in the presence of a CI, especially in case of skull base diseases requiring MRI monitoring.