Computed tomography and lameness diagnosis (What does it mean? Significance of radiographic changes in the limb)

From a historical perspective, in medical imaging, computed tomography (CT) pre-dates magnetic resonance imaging (MRI) and therefore many orthopaedic applications for CT were described initially. As MRI became more common in the clinical setting, its use has largely usurped CT, particularly in the diagnosis of soft tissue musculoskeletal injuries. It is generally accepted that CT can yield more information regarding the morphology of bone but soft tissue detail of MRI is superior. In equine veterinary medicine, many reports tout the clinical utility of MRI particularly for the diagnosis of tendon, ligament and joint injuries causing lameness arising from the distal limb [1–3].
Computed tomography has been reported for the same purpose but to a lesser extent [4–6]. Computed tomography images are produced as an x-ray generating tube located across from a row of x-ray detectors in a circular gantry, rotates around the anatomic region of interest. A modern, helical scanner will have continuous x-ray tube rotation as the patient is transported through the centre of the gantry, thus producing a helical path of x-rays. A multislice helical scanner houses multiple detector rows across from the x-ray tubes in order that multiple slices of the anatomy can be made contemporaneously. Images depict differences in tissue density and are analogous to cross-sectional radiographs. A modern, multi-slice, helical scanner is capable of very rapid image acquisition of thin (sub 1 mm) slices. Computed tomography produces images that represent the regional anatomy and changes in morphology are necessary to identify injury. In order for a tendon tear to be identified on CT it must be sufficiently large and cause enough of a change in density to be detected by the scanner. The identification of lesions is aided by the recognition of other additional basic imaging (roentgen) findings such as changes in size, shape and margination. […]