Pre- and Postoperative Imaging of Cochlear Implantation in Cadaveric Specimens Using Low-Dose Photon-Counting Detector CT

Bjoern Spahn, Franz-Tassilo Müller-Graff, Kristen Rak, Jonas Engert, Johannes Voelker, Stephan Hackenberg, Rudolf Hagen, Tilmann Neun, Bernhard Petritsch, Thorsten Alexander Bley, Jan-Peter Grunz and Henner Huflage

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Abstract

BACKGROUND AND PURPOSE: Anatomically adapted cochlear implantation and efficient postoperative cochlear implant-fitting strategies benefit from reliable and highly detailed imaging techniques. Since image quality in CT is related to the applied radiation dose, this study aimed to evaluate low-dose cochlear imaging with a photon-counting detector by investigating the accuracy of pre- and postoperative cochlear analysis.

MATERIALS AND METHODS: Photon-counting CT images of 10 temporal bone specimens were acquired with 3 different radiation dose levels (regular dose: 27.1 mGy, low dose: 4.81 mGy, and ultra-low dose: 3.43 mGy) before and after cochlear implant electrode carrier insertion. A clinical scan protocol was used with a tube potential of 120 kV in ultra-high-resolution scan mode (detector collimation 120 × 0.2 mm). The accuracy of cochlear duct length measurements for the organ of Corti and electrode contact determination was investigated for all applied settings by 2 independent otosurgeons.

RESULTS: No substantial differences were ascertained between photon-counting CT scans performed with standard dose and dedicated low-dose imaging regarding the accuracy of neither pre- and postoperative cochlear analysis nor postoperative cochlear implant electrode analysis. Radiation dose reduction of 82.3% (low dose) and 87.3% (ultra-low dose) could be realized compared with the clinical standard protocol.

CONCLUSIONS: Ultra-high-resolution cochlear imaging is feasible with very low radiation exposure when using a first-generation photon-counting CT in combination with dedicated low-dose protocols. The accuracy of pre- and postoperative cochlear analysis with the applied dose reduction settings was comparable with a clinical regular-dose protocol.

ABBREVIATIONS:

AID
angular insertion depth
CDL
cochlear duct length
CDLLW
cochlear duct length of the lateral cochlea wall
CDLOC
cochlear duct length of the organ of Corti
CTDIvol
volume CT dose index
DLP
dose-length product
EID
energy-integrating detector
ICC
intraclass correlation coefficient
IL
insertion length
LD
low dose
PCD
photon-counting detector
RD
regular dose
SD
standard deviation
ULD
ultra-low dose
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