Quantitative Analysis of the Cochlea using Three‐Dimensional Reconstruction based on Microcomputed Tomographic Images

Abstract

The aim of this study was to provide data on various dimensions of the normal cochlea using three-dimensional reconstruction based on high-resolution micro-CT images. The petrous parts of 39 temporal bones were scanned by micro-computed tomography (CT) with a slice thickness of 35 lm. The micro-CT images were used in reconstructing three-dimensional volumes of the bony labyrinth using computer software. The volumes were used to measure 12 dimensions of the cochlea, and statistical analysis was carried out. The dimensions of cochleae varied widely between different specimens. The mean height and length of the cochlea were 3.8 and 9.7 mm, respectively. The angle between the basal and middle turns was slightly larger in males than in females, while none of the other 11 dimensions differed significantly between males and females. The cochlear accessory canals were observed in about half of the cases (51.3%). Correlation analysis among measured items revealed positive correlations among several of the measured dimensions. The present study could investigate the detailed anatomy of the normal cochlea using high-resolution imaging technologies. The results of the present study could be helpful for the precise diagnosis of congenital cochlear malformations and for producing optimized cochlear implants.

Automated analysis of human cochlea shape variability from segmented μ CT images

“…A normal distribution was fit to the concatenated data. Comparing the results of this current study with previous findings shows that, on one hand the mean number of cochlear turn (2.58) falls extremely close to the mode of the normal distribution (2.59), on the other hand the standard deviation (0.28) is broader than what is found in the literature (0.11 (Kawano et al, 1996), 0.09 (Shin et al, 2013), 0.17 (Avci et al, 2014)). This result could be explained by the presence of two extreme cases.…”

“…This model could be used to provide prior anatomical information required for analyzing clinical CT images. Indeed due to spatial resolution limitation, conventional CT images alone cannot provide enough fine information about anatomical structures relevant for cochlear implantation (Shin et al, 2013). Specifically the basilar membrane that delimits the scala tympani is nearly invisible with clinically available imaging techniques.…”

“…When the number of cochlear turns is not specifically detailed (Kawano et al, 1996;Braun et al, 2012;Kjer et al, 2015), many authors transcribed the mean, the standard deviation, the range and the number of the measurements (Erixon et al, 2009;Shin et al, 2013;Avci et al, 2014). For illustration purposes, Fig.…”

“…As important cochlear anatomical structures such as the basilar membrane are not visible in CT imaging, analyses of the cochlea are commonly performed using µCT images (Verbist et al, 2009;Poznyakovskiy et al, 2011;Gunz et al, 2012;Shin et al, 2013;Avci et al, 2014;Ceresa et al, 2014). In order to improve contrast, temporal bone samples can be fixed and stained before imaging (Poznyakovskiy et al, 2011).…”

“…Previous analyses include measurements of the length of the cochlea and the number of cochlear turns (Hardy, 1938;Kawano et al, 1996;Skinner et al, 2002;Escudé et al, 2006;Stakhovskaya et al, 2007;Erixon et al, 2009;Gunz et al, 2012;Shin et al, 2013;van der Marel et al, 2014), measurements of the heights, widths and sectional areas of the scala tympani (Zrunek et al, 1980;Zrunek and Lischka, 1981;Hatsushika et al, 1990;Gulya and Steenerson, 1996;Wysocki, 1999;Thorne et al, 1999;Biedron et al, 2010;Avci et al, 2014), the scala vestibuli (Zrunek and Lischka, 1981;Gulya and Steenerson, 1996;Wysocki, 1999;Thorne et al, 1999;Biedron et al, 2010) and the cochlea (Erixon et al, 2009;Shin et al, 2013), measurements of the radial component of the cochlear centerlines (also called cochlear curvature) (Cohen et al, 1996;Baker, 2008;van der Marel et al, 2014), and studies of the longitudinal component of the centerlines of the scala tympani (Avci et al, 2014) and the cochlea itself (Verbist et al, 2009).…”