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. 2016 Dec;37(10):1560-1564.
doi: 10.1097/MAO.0000000000001245.

Evaluation of Rigid Cochlear Models for Measuring Cochlear Implant Electrode Position

Ahmet Cakir  1 , Robert F Labadie, M Geraldine Zuniga, Benoit M Dawant, Jack H Noble
Affiliations

Evaluation of Rigid Cochlear Models for Measuring Cochlear Implant Electrode Position

Ahmet Cakir et al. Otol Neurotol. 2016 Dec.

Abstract

Objective: To investigate the accuracy of rigid cochlear models in measuring intra-cochlear positions of cochlear implant (CI) electrodes.

Patients: Ninety three adults who had undergone CI and pre- and postoperative computed tomographic (CT) imaging.

Main outcome measures: Seven rigid models of cochlear anatomy were constructed using micro-CTs of cochlear specimens. Using each of the seven models, the position of each electrode in each of the 98 ears in our dataset was measured as its depth along the length of the cochlea, its distance to the basilar membrane, and its distance to the modiolus. Cochlear duct length was also measured using each model.

Results: Standard deviation (SD) across rigid cochlear models in measures of electrode depth, distance to basilar membrane, distance to modiolus, and length of the cochlear duct at two turns were 0.68, 0.11, 0.15, and 1.54 mm. Comparing the estimated position of the electrodes with respect to the basilar membrane, i.e., deciding whether an electrode was located within the scala tympani (ST) or the scala vestibuli (SV), there was not a unanimous agreement between the models for 19% of all the electrodes. With respect to the modiolus, each electrode was classified into one of the three groups depending on its modiolar distance: close, medium, and far. Rigid models did not unanimously agree on modiolar distance for approximately 50% of the electrodes tested.

Conclusions: Inter-model variance of rigid cochlear models exists, demonstrating that measurements made using rigid cochlear models are limited in terms of accuracy because of non-rigid inter-subject variations in cochlear anatomy.

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Conflict of interest statement

Conflicts of Interest/Disclosures: Dr. Labadie is a consultant for Advanced Bionics, and Ototronix.

Figures

Figure 1
Figure 1
Two different views of a cropped μCT image where scala tympani (ST), scala vestibuli (SV) and modiolus are represented with light blue, yellow and red contours, respectively
Figure 2
Figure 2
Rigidly model fitting result. Scala tympani (ST - red) and modiolus (blue) are the surfaces in the pre-implantation CTs, and ST (green) and modiolus (yellow) belong to one of the rigid models
Figure 3
Figure 3
Segmentation of anatomical structrues using 7 different rigid models are represented with 7 different colors. Scala Tymani (ST) on the left, Scala Vestibuli (SV) in the middle, and modiolus on the right
Figure 4
Figure 4
The basilar membrane curve (BMC) that separates scala tympani (ST) and scala vestibuli (SV) is shown in white. ST and SV are shown as blue and green 3D meshes, respectively
Figure 5
Figure 5
Scala tympani (ST) is shown as the blue 3D mesh. Mid-modiolar axis, m and s vectors are in red, light blue and yellow, respectively
See this image and copyright information in PMC

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