Alonso, J.M., Degollada, E., Delory, E., André, M. Odontocete Ear Analysis by Imaging Techniques 17 th Annual Conference of the European Cetacean Society, Las Palmas de Gran Canaria, 2003 Resum: The increasing level of knowledge on the effect of underwater noise on the marine environment has lead to the necessity of studying the odontocete ear. However, the complicated access of the ears in those species together with their structure make difficult the use of conventional invasive methods, implying complex processing and interpretation of the results. Non-invasive imaging techniques as computed tomography (CT) and magnetic resonance imaging (MRI) appear to be an alternative to analyze the odontocete middle and inner ear structures, and the viability of these techniques could be explored both in vivo and post-mortem studies. With the purpose of describing the odontocete ear morphology, general CT and MRI were performed in 4 dead stranded dolphins in extremely fresh conditions. The extracted ears were analyzed with two spectrometers Bruker of 200Mhz/ 4.7 Teslas and 400Mhz/ 9.4 Teslas respectively. As already described for these imaging techniques, bony structures and their boundaries, including middle ear and auditory ossicles, are better visualized with CT scans. High magnetic field MRI units allow an increase of the image resolution but imply consequent long acquisition times and small sample sizes. Inner ear major structures were identified with the latter techniques - i.e. the cochlear scalae, the spiral ganglion and ligament, the organ of Corti - although the scans did not provide a good microscopic structure image, meaning a necessary posterior histological analysis. Those limiting factors restrain to macroscopic lesions the possibility of using these techniques for the diagnostic of ear pathologies. The planned development of MRI and CT units – e.g. power increase, accurate process parameters definition and acquisition times reduction - will provide images at cellular level, reducing the artifacts associated with complex histological processing and confirming the possibility of using these non-invasive techniques as an objective diagnostic tool both in dead and live animals.