Evaluation von Artefakten von Cochleaelektroden der Firma Cochlear in der digitalen Volumentomographie
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Philipps-Universität Marburg
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Abstract
Through the development of the cochlear implant (CI), it is possible for the first time in medicine to replace a non-functional sensory organ in order to generate a
hearing impression in patients. This work concentrates on the display of intracochlear electrodes using cone beam computed tomography (CBCT). The CI guideline recommends postoperative imaging to confirm the correct position of the electrode arrays in the cochlea and to detect possible misinsertions and scale changes. Furthermore, imaging also plays an important role in the scientific development of the cochlear implant. By comparing the position of the electrodes with the achieved hearing performance, an optimized localization of the electrode can be achieved. As an option to conventional computed tomography (CT), CBCT offers a lowradiation, cost-effective and time-saving alternative. Regarding examinations of high density structures such as the temporal bone, CBCT is superior to CT. A
possible dose reduction by CBCT is of great relevance, especially concerning radiation protection in examinations of younger patients. A total of four whole-head preparations were used and implanted with various cochlear implants from Cochlear®. The implants used differ in the structure and behavior in the cochlea. Two of the CI are straight, while the other two are curved (Contour Advance). The curved electrodes of the Contour Advance group are intended to achieve a position close to the modiolus. After implantation, the implant electrodes were visualized by CBCT. The radiological diameters (artefact) of the electrodes 1, 11 and 20 were measured and their position in the cochlea was determined. Furthermore, under varying x-ray tube adjustments the recorded electrode size was examined with the question of whether a dose reduction in postoperative diagnostics can be achieved in everyday clinical practice. Subsequently, the radiologically determined diameters were compared with the actual dimensions. The results of this work demonstrate that the breadth of the cochlea decreases in its course from basal to apical in each whole-head specimen. There is a significant difference in the intracochlear position of the different CI. While the electrodes of the Contour Advance series are located perimodular, those of the straight electrode arrays are localized far from the modiolus. For all electrodes, an artefact size between 50 and 70 % was found. An increase of the artefact size from basal (electrode 1 approximately 50 %) to apical (electrode 21 approximately 70 %) was observed. The artefact size depends on in which plain the electrodes were measured. Often, the visualization of electrodes in the medial and apical coils of the cochlea is limited due to artefact overlays. Interestingly, there was no dependence of the artefact on the applied dose. The artefact size remained constant even under reduced radiation dose.
In summary, due to better visualization of high-density structures and lower radiation exposure, CBCT is the preferred choice for postoperative monitoring of
cochlear implant electrodes. Furthermore, the results show that theoretically a radiation dose reduction up to 45 % of the initial value would be possible to obtain
a precise localization of the electrodes within the cochlea, whereby examinations of the effect on image quality still have to be carried out.
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Created: 2019Issued: 2019-04-08Updated: 2019-04-08
Faculty
Medizin
Publisher
Philipps-Universität Marburg
Language
ger
Data types
DoctoralThesis
DFG-subjects
Cochlea-Implantat DVT Elektroden Artefakt Cochlea Strahlendosis Postoperative Bildgebung Intracochleäre Lage Elektrodenartefakt
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610
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Bevis, Nicholas Frederick: Evaluation von Artefakten von Cochleaelektroden der Firma Cochlear in der digitalen Volumentomographie. : Philipps-Universität Marburg 2019-04-08. DOI: https://doi.org/10.17192/z2019.0198.
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