Advantages and limitations of X-ray and computed tomography systems for the study of the skeleton in meagre (Argyrosomus regius)

Abstract

Several methods and procedures exist for the diagnosis of skeletal disorders in fish. X-ray is one of the most reliable diagnosis technologies for medium-sized and large animals, whereas external examination is only of value in animals with extreme and prominent deformities. In small fish (e.g. juveniles or larvae), whole mount staining with alizarin red and/or alcian blue is advisable, although soft-tissue X-ray may be also used. Under this context, the study of the fish skeleton and its morphological and developmental disorders requires an accurate visualization of three-dimensional structures, but few widely applicable methods exist for non-destructive whole-volume imaging of animal tissues. In this sense, computed tomography (CT) has been recently suggested as an alternative or complementary imaging method for the early diagnosis of skeletal deformities, as well as a valuable tool for the current research on the causes and prevention of these anatomical disorders. In this study, we have analysed the skeleton of a 9.3 kg meagre (Argyrosomus regius) by means of standard X-rays (SEDECAL APR-VET 20 KW) and computerized X-ray tomography (HiSpeed Zx/i, General Electric Healthcare) and compared both imaging methods. The vertebral column of the examined specimen was composed by 24 vertebral bodies (including the urostyle) with a regional variation in the morphology of centrums along the vertebral axis. Both imaging methodologies allowed the clear visualization and identification of bony structures composing the skeleton of the meagre. In addition, the CT also allowed performing axial cuts of the meagre in which it was possible to differentiate tissues of different density (e.g. muscle, fat, bone), due to their different attenuation of the X-rays measured in Hounsfield scale. A general view of the potential of such imaging techniques, considering both their advantages and limitations is discussed.