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Scalar Position of the CI electrode array: An analysis of the evaluation quality of different imaging systems
18 April 2018 (online)
Hearing preservation in CI implantation requires preservation of the inner ear structures. The hearing result depends on the correct position of the CI electrode. To make valid statements about the role of the scalar position, a reliable assessment of the post-op imaging is necessary. The high variability of the incidence of a scalar displacement may indicate an assessment problem.
56 post-op DVT Scans were assessed by 3 radiologists and one CI surgeon. The quality of the imaging, the precision of the evaluation of the scalar position of the CI array (each contact) and the results between the investigators were compared.
For evaluation the post-op DVT was used either alone, or a fusion of the DVT with a pre-operative MRI (1.5 Tesla or 3 Tesla) were compared.
The results show a high uncertainty in the assessment of the scalar position when using DVT alone, the results between the experts show a high variance. The overall rate of scalar displacement is well below the rate when using fused images.
When using the 1.5 Tesla MRI, the quality of assessment could be increased, but no complete concordance is achieved between the investigators.
The fusion with 3 Tesla MRI, provided a reliable assessment by all investigators, the highest rate of scalar dislocation, and an almost 100% confidence in the assessment of each electrode contacts.
The assessment quality of the CI electrode position must be critically examined. Mono-modal imaging does not have a sufficient evaluation quality. For scientific purposes, only the fusion with MRI images is sufficient to obtain reproducible results. According to this study, the high variability of the scalar dislocation rates in the literature must be attributed primarily to an inaccurate assessment.