IMAGING IN HOOFED MAMMALS' DISTAL LIMB ... variety of captive hoofed mammals. ... Seventy nine captive wild odd-toed ungulates (Perissodactyla) and ...
SYNCHRONIZED COMPUTED TOMOGRAPHY-DIGITAL RADIOGRAPHY IMAGING IN HOOFED MAMMALS’ DISTAL LIMB Galateanu G1, Szentiks CA1, Mezö Z1, Strauß G2, Bertelsen MF3, Hildebrandt TB1 1
Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany, 2Tierpark Berlin, Berlin, Germany, Copenhagen Zoo, Copenhagen, Denmark.
Background: Chronic foot disease represents a tremendous clinical challenge and is a major health concern for herbivores in captivity, often being a reason for euthanasia. Currently, radiography is the only imaging technique used to diagnose bone pathology in animals under “field conditions”. Yet, unlike in elephants for which numerous studies exist, keystone data, such as normal foot radiographic appearance is very scarce for other hoofed mammals. The current assumption is that the anatomy of wild herbivores can be extrapolated from their domestic relatives. Purpose: This study was designed to identify and depict normal radiographic appearance of distal foot in a wide variety of captive hoofed mammals. Methods: Using state-of-the-art tools of 128-slice computed tomography (CT) and a dedicated workstation, the authors initiated a pioneering approach termed ‘synchronized CT - digital radiography (DR), (Synch DR)’ based on X-ray projections derived from tri-dimensional (3D) CT reconstructed images. For each foot studied, eight 3D CT images (45° apart), equivalent to eight standard radiographic views, together with additional projections were obtained. Each such 3D CT image was transformed into a Synch DR image and the following autopodial elements were analyzed: podial elements, metapodials and phalanges. Distal limb excerpts were collected after the unrelated death of the animals, in the context of mandatory post mortem examination and disease diagnosis. Seventy nine captive wild odd-toed ungulates (Perissodactyla) and even-toed ungulates (Artiodactyla) from a wide variety of species and subspecies (n) were encompassed in our study. The order Perissodactyla included all extant families: Equidae (n=3), Tapiridae (n=2) and Rhinocerotidae (n=2). Artiodactyla’s order included: Suidae (n=2), Tayassuidae (n=1), Hippopotamidae (n=2), Tragulidae (n=1), Camelidae (n=4), Giraffidae (n=3), Cervidae (n=6) and Bovidae (n=15). Findings: High resolution CT-DR synchronization: (1) depicted normal anatomic features and their radiographic appearance for each foot in eight radiographic views; (2) showed that species dependent anatomical variations must be taken into account, emphasizing the unique traits found in each taxa; (3) endowed us with key radiographic knowledge from many endangered species, with a limited number of captive individuals; (4) enabled the identification of species dependent radiographic views, that allow a better visualization of autopodial elements than the traditional orthogonal and oblique projections. Distinct anatomical differences were found between the domestic and wild species both in Perissodactyla and Artiodactyla orders (e.g. Equidae, Hippopotamidae, Bovidae). Furthermore, noticeable autopodial dissimilarities were found between two wild species belonging to the same taxonomic family (e.g. Southern white and Indian rhinoceroses). Conclusions: This study provides important reference data on radiographic appearance of normal anatomy; taxa-specific, optimal radiographic views for better autopodial visualization; and comparative radiographic anatomy results in hoofed mammals’ distal limb. Such major advances in diagnostic imaging facilitate straightforward implementation and easy interpretation of ungulate foot radiographic images taken in the field worldwide.