الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
After cochlear implantation thorough follow up sessions are needed to ensure optimal results and during these sessions electrode position and performance are two extremely important factors. Previously, this was done by plain x-rays then MSCT was the gold modality but then CBCT started to immerge as a promising alternative.
Its stated that great isotropic spatial resolution, fairly low dose requirements, low cost, and ease of access have all made it particularly appealing. By applying a reduced radiation dose, CBCT can provide high-resolution pictures and demonstrate benefits for examining bony features of the inner ear. The potential of CBCT adoption in otorhinolaryngology, particularly in the field of otology, has aroused enthusiasm.
To create a diagnostically acceptable and interpretable image, the appropriate FOV, milliamperes (mAs), and kilovolts (kVp) settings, as well as high definition/high resolution parameters, should be determined based on the scan’s indication. This must adhere to ALARA’s radiation dose principle: ”as low as reasonably achievable.” A new ALADA idea has been developed, which is a variant of ALARA and stands for ”as low as diagnostically acceptable.”
In this study, we used CBCT for assessment of scalar location, insertion length and distance between the cochlear implant electrode array and modiolus and correlated these factors to speech performance.
The current study was conducted on 30 selected patients who came to the outpatient clinic of the department of Otolaryngology of Alexandria University as to keep as many confounding factors constant. This study was carried out on 30 children with bilateral severe to profound prelingual sensorineural hearing loss that had undergone cochlear implantation.
All participants in this study were subjected to history taking, clinical assessment, and acquisition of CBCT of the inner ear structures, and audiological evaluation. All scans were evaluated by expert radiologist. The CBCT images were viewed using OnDemand3D™ software from Cyber-med Inc. CBCT images were analyzed regarding the visibility of the important anatomical parameters of the ear, electrode arrays position and correlated with speech recognition score.
In the present study, we found a strong negative correlation between distance to modiolus and performance scores that were statistically significant. By correlating with the respective scores and analyzing the data we found that the smaller the perimodiolar distance the better the performance of the subject, namely if less than 0.45 mm performance would be equal to or above 80 % in child scores.
CBCT revealed that the electrode array was inserted in the scala tympani in 26/30 children (86.66%) and showed a better speech recognition score than scala vestibule insertion. The mean distance between the modiolus and electrode arrays was 0.53 ± 0.11 mm and the average length of insertion was 21.49 ± 3.65mm.. Pearson test showed a statistically significant positive correlation between insertion length and speech recognition score.
In conclusion, CBCT is an excellent tool for inner ear and CI imaging and may as well replace MSCT. Perimodiolar distance and insertion depth are very good indicators of actual performance of a patient with CI and could be used clinically for this role. As there is no prior research done in this area, we recommend further similar studies using more advanced scanners and greater pool of patients as well as to use such technique for post-operative follow up.