Improved Cochlear Implant Position Detection with Spatially Synchronized Pre- and Post-Operative Midmodiolar Cross-Section CT and MR Images

Background: Prevention of insertion trauma is a general goal in cochlear implantation. In vivo evaluation of intrascalar position of a cochlear implant electrode array provides surgical feedback but is challenging due to scattering effects of the electrode array.

Objective: This study introduces an evaluation method using spatially synchronized pre- and post-operative midmodiolar cross-section CT and MR images.

Methods: Three observers scored the intra-scalar position of all electrode contacts of 15 HiFocus 1J and 15 HiFocus Mid-Scala electrode arrays using three different methods; on midmodiolar cross-section post-operative CT images only and supported with spatially synchronized pre-operative CT and MR images. The intra- and inter-observer coefficients were calculated and compared between the methods.

Results: Using spatially synchronized pre-operative images, increases inter-observer coefficients in the 1 J population from 0.75 with the use of post-operative CT only to 0.79 and 0.80 with the use of pre-operative CT and MRI respectively. In the MS population an increase from 0.77 to 0.83 (CT and MRI) was found. For the intra-observer correlation coefficients, an increase from 0.72 to 0.81 (CT) and 0.82 (MRI) in the 1J population and from 0.72 to 0.86 (CT) and 0.84 (MRI) in the MS population were seen. No difference between the use of CT and MR images was found. A linear mixed model analysis revealed the significant effect of angular insertion depth on the inter- and intra-observer coefficients in the MS population only.

Conclusion: Using a referential pre-operative CT or MRI scan improves the determination of cochlear implant electrode array position.