Tomographic imaging in companion avian species

Background In the last decades an increasing number of publications, proposing both clinical trials and diagnostic tests, have become available on avian medicine. Despite all the new technical advances the diagnosis and treatment of avian patients is still challenging for the veterinary clinician because birds often display only vague and non-specific symptoms of disease and the investigation of the underlying causes is often very frustrating. In such a scenario diagnostic imaging plays a fundamental role in the clinical evaluation of avian patients. Results The result of this PhD research is an atlas of the tomographic anatomy of three avian species. Most of the clinically relevant structures of the head were visible in both the cross-sections and corresponding CT images. The thin trabeculae characterizing the avian skull were optimally visible on CT images when a standard soft tissue filter and pulmonary window was used. The same CT settings allowed clear visualization of the nostrils, operculum, infraorbital sinus, and cervicocephalic air sacs. The nasal septum, conchae, scleral ossicles, interorbital septum, auditory meatus, and hyoid skeleton were clearly identifiable when a high-resolution filter and bone window were used. Reconstruction of CT images in a dorsal plane enabled a more comprehensive visual examination of some complex structures of the head, such as the diverticula of the infraorbital sinus and the periorbital muscles and glands. 6 Structures of the inner ear were not visible in the anatomic cross-sections nor in the CT scans of any of the examined parrot species. A standard soft tissue filter with a soft tissue window allowed a good visibility of the eyes and related structures in all examined species. The cerebral hemispheres, cerebellum, and medulla oblongata were distinguishable only on anatomic cross-sections, and all had the same soft tissue attenuation. All the main organs of the respiratory, digestive, urinary (including the ureters) and reproductive systems were visible both in the anatomical sections and in the corresponding CT images. Conclusions CT is a fast, safe and reliable diagnostic test for avian patients. The possibility to scan the entire body, avoiding the superimposition of the radiography is a great improvement in the diagnostic process. Furthermore, the use of contrast medium allowed optimal visibility of the soft tissues. Those findings suggested that the complex nature of the avian anatomy make CT the diagnostic imaging technique of choice for the evaluation of both the coelomic cavity and the head of avian patients. The matched anatomical cross-sections and CT images presented in this study are a useful reference for the interpretation of CT examination of the blue-and-gold macaw, African grey parrot and monk parakeet. This atlas can be used also for the interpretation of CT images obtained in other psittacine species but the clinicians should be aware of the anatomical differences occurring between the species investigated in these studies and the species object of the investigation. For this reason, further studies, including a larger number of both 7 psittacine and non-psittacine species are desirable for a more comprehensive description of the CT anatomy of avian patients.