A retrospective analysis of the IC using routine MRI-image stacks from patients of the Regensburg University Hospital ENT department

MRI-image stacks from patients of the Regensburg University ENT department were retrospectively used to analyze the inferior colliculus (IC). Image stacks and the related DICOM files from 66 patients were included in the present analysis.

Screenshots of the MRI image layers were transferred from the SAP software MPRAGE MRI as a stack of images into ImageJ and adequately scaled. Using the “orthogonal view” mode the IC was identified in the different projections and voxels belonging to the IC were manually labelled as “Region of Interest” (ROI) to determine the number of voxels belonging to the left and right IC respectively. IC-volume was calculated by multiplying the number of voxels with the voxel-volume which was derived for each image-stack from “slice thickness” (0.7-1.1mm) and “pixel spacing” (0.78-1.02mm) recorded in the corresponding DICOM file.

The IC-volume varies systematically with age (Kruskal-Wallis-Test, comparing the effect of age group on IC-volume, p<0.001). Subsequent Mann-Whitney-U-tests showed significant increases (p<0.001) of mean IC-volume from group1, infants below 1 year of age (15.3+/-3.9mm³; N = 23) to group 2, children between 1 and 10 years (21.5+/-6.7mm³, N = 17) and group 3, juveniles and adults between 10 and 60 years (29.1+/-6.1mm³, N = 19). Compared to group 3, IC-volume was significantly reduced in group 4 with age over 60 years (22.0+/-3,1mm³, N = 7, p<0.007).

The volume of the human IC can be determined from routine clinical MRI image stacks. The pattern of age dependent variation of IC-volume closely resembles data published by Koenigsmark and Murphy (1972) for the human ventral cochlear nucleus. The reduction of IC-volume at high age in humans is consistent with findings in aged gerbils (Gleich, Netz, Strutz; 2014).

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Artikel online veröffentlicht:
10. Juni 2020