Cochlear duct length measurement dependent on varying radiation doses in a photon-counting CT
B. Spahn, H. Huflage, JP. Grunz, B. Petritsch, FT. Müller-Graff, J. Völker, R. Hagen and K. Rak
Introduction
Precise knowledge about the cochlear duct length (CDL) is necessary for an individualized selection and implantation of the CI electrode carrier. The level of detail of the preoperative imaging modality depends on the selected radiation dose and examination time of the CT imaging. In previous studies, an impressive reduction of the radiation dose in a photon-counting CT could be demonstrated, compared to a conventional CT scan. The aim of the work was to evaluate the dependency of the CDL measurements in a photon-counting CT at different radiation doses using the OTOPLAN software (MED-EL) and 3D-curved multiplanar reconstruction.
Methods
5 human cadaveric body donors were examined with scan modes of a photon-counting CT. Different radiation doses were applied measured by the Computed Tomography Dose Index (CTDI). A reference scan for an high image quality was performed with a CTDI of more than 150 mGy. According to the study protocol, imaging was done with descending CTDIs of 27.1 mGy, 7.6 mGy and 4.8 mGy. Afterwards, measurement of the CDL with the OTOPLAN Software, ECA-formular and 3D-curved multiplanar reconstruction was performed. For comparison purposes a conventional CT scan with a radiation exposure of up to 47.32 mGy was used.
Results
Different radiation doses in a photon-counting CT led to only slight differences of the CDL measurement, with a maximum deviation of 0.8 mm measured by MPR technique. ECA-formula and Otoplan® software showed minor, non-significant differences of the CDL.
Conclusion
Preoperative measurement of the CDL in a photon-counting CT showed no significant differences when using different radiation doses and when measurement was performed by ECA-formula and Otoplan® software. Preliminary work had already shown that a slice thickness of the imaging dataset of 0.4 mm is too big for an accurate MPR analysis, which may explain CDL differences measured by MPR technique in this work. Photon-counting CT is a promising alternative to a conventional EID-CT scan in terms of low dose radiation. Further investigations of the photon counting CT will show, how CDL measurement can be performed with imaging datasets with inserted CI electrodes.

**Cochlear duct length measurement dependent on varying radiation doses in a photon-counting CT**
B. Spahn, H. Huflage, JP. Grunz, B. Petritsch, FT. Müller-Graff, J. Völker, R. Hagen and K. Rak
**Introduction**
Precise knowledge about the cochlear duct length (CDL) is necessary for an individualized selection and implantation of the CI electrode carrier. The level of detail of the preoperative imaging modality depends on the selected radiation dose and examination time of the CT imaging. In previous studies, an impressive reduction of the radiation dose in a photon-counting CT could be demonstrated, compared to a conventional CT scan. The aim of the work was to evaluate the dependency of the CDL measurements in a photon-counting CT at different radiation doses using the OTOPLAN software (MED-EL) and 3D-curved multiplanar reconstruction.
**Methods**
5 human cadaveric body donors were examined with scan modes of a photon-counting CT. Different radiation doses were applied measured by the Computed Tomography Dose Index (CTDI). A reference scan for an high image quality was performed with a CTDI of more than 150 mGy. According to the study protocol, imaging was done with descending CTDIs of 27.1 mGy, 7.6 mGy and 4.8 mGy. Afterwards, measurement of the CDL with the OTOPLAN Software, ECA-formular and 3D-curved multiplanar reconstruction was performed. For comparison purposes a conventional CT scan with a radiation exposure of up to 47.32 mGy was used.
**Results**
Different radiation doses in a photon-counting CT led to only slight differences of the CDL measurement, with a maximum deviation of 0.8 mm measured by MPR technique. ECA-formula and Otoplan® software showed minor, non-significant differences of the CDL.
**Conclusion**
Preoperative measurement of the CDL in a photon-counting CT showed no significant differences when using different radiation doses and when measurement was performed by ECA-formula and Otoplan® software. Preliminary work had already shown that a slice thickness of the imaging dataset of 0.4 mm is too big for an accurate MPR analysis, which may explain CDL differences measured by MPR technique in this work. Photon-counting CT is a promising alternative to a conventional EID-CT scan in terms of low dose radiation. Further investigations of the photon counting CT will show, how CDL measurement can be performed with imaging datasets with inserted CI electrodes.

Cochlear duct length measurement dependent on varying radiation doses in a photon-counting CT 

It is with great pleasure and enthusiasm, that on behalf of the Cochlear Implant centers of the Radboud UMC in Nijmegen and Erasmus MC Sophia Children’s Hospital in Rotterdam to invite you to attend the 16th European Symposium on Pediatric Cochlear Implantation to Rotterdam, the Netherlands in 2023.

Yours sincerely, on behalf of the CI Centers at Radboud UMC and Erasmus MC,