Characterization of Normal Bone in the Equine Distal Limb with Effective Atomic Number and Electron Density Determined with Single-Source Dual Energy and Detector-Based Spectral Computed Tomography

Simple Summary Diseases involving the subchondral bone are common in horses and are usually evaluated with conventional imaging techniques, such as radiography, conventional computer tomography, and magnetic resonance imaging. Characterization of the normal subchondral bone as well as exercise-related changes is of special interest in ongoing research. Single-source dual energy and detector-based spectral computed tomography are emerging technologies allowing the characterization of tissues that have different attenuation properties at different energies. Both technologies enable the calculation of effective atomic number, an index to determine tissue composition, and electron density, which is assumed to be associated with cellularity in tissues. In the present study, both values were determined in normal subchondral and trabecular bones in the distal limb of horses with single-source dual energy and detector-based spectral computed tomography. Several effective atomic number and electron density values differed between both technologies and within and between bones of the distal equine limb with both technologies. Effective atomic number values increased with age in the palmar/plantar fetlock joint zone. The reported effective atomic number and electron density values in the subchondral and trabecular bone of the equine distal limb may serve as preliminary reference values and aid future classification of diseases.Abstract Single-source dual energy (SSDECT) and detector-based spectral computed tomography (DBSCT) are emerging technologies allowing the interrogation of materials that have different attenuation properties at different energies. Both technologies enable the calculation of effective atomic number (EAN), an index to determine tissue composition, and electron density (ED), which is assumed to be associated with cellularity in tissues. In the present prospective observational study, EAN and ED values were determined for 16 zones in normal subchondral and trabecular bone of 37 equine cadaver limbs. Using both technologies, the following findings were obtained: 1. palmar/plantar EAN zone values in the fetlock increased significantly with increasing age of the horse; 2. all EAN and ED values were significantly lower in the trabecular bone than in the subchondral bone of all phalanges; 3. in the distal phalanx and navicular bone, most EAN and ED values were significantly lower compared to the proximal and middle phalanx; and 4. some EAN and ED values were significantly different between front and hind limbs. Several EAN and ED values significantly differed between SSDECT and DBSCT. The reported EAN and ED values in the subchondral and trabecular bone of the equine distal limb may serve as preliminary reference values and aid future evaluation and classification of diseases.