Differences between µCT-imaging and conventional CT for the diagnosis of possible diseases of the middle and inner cat ear.

The aim of this study was to check the relevance of using in-vivo micro computed tomography (µCT) for the diagnosis of possible diseases of the middle and inner ear of the cat. Therefore, on the one hand, differences of the detail detectability between the two imaging methods conventional computed tomography (cCT) and in-vivo µCT were analyzed. Six healthy cat ears were dissected and scanned several times and the obtained images were compared with each other. On the other hand, histological slices of all ears were prepared and pictures of defined anatomical structures were taken and compared with the identical sectional plane of the µCT-images. This way it was possible to evaluate the quality and clinical limitations of the in-vivo µCT. The results show that an in-vivo µCT is suitable to analyze even the smallest osseous structures, such as the semicircular ducts, the spiral osseous lamina or the ossicles whereas with the help of cCT it is not possible to identify such small osseous structures because of their blurred and less detailed representation. Delicate soft tissue structures as the membranous labyrinth including hearing and vestibular organ cannot be differentiated with as well in-vivo µCT- as with cCT-images. In-vivo µCT represent a good possibility for more detailed diagnosis of extremely fine structures which cannot be detected with cCT. Histological slices can nonetheless not be replaced by in-vivo µCT due to a too low spatial resolution and the limitations of the in-vivo µCT with regard to the evaluation of soft tissue dense structures.