Radiology
MRI uses strong magnetic fields to align atomic nuclei (usually hydrogen protons) within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the radio frequency signal generated as the nuclei return to their baseline states. The radio signals are collected by small antennae, called coils, placed near the area of interest. An advantage of MRI is its ability to produce images in axial, coronal, sagittal and multiple oblique planes with equal ease. MRI scans give the best soft tissue contrast of all the imaging modalities. With advances in scanning speed and spatial resolution, and improvements in computer 3D algorithms and hardware, MRI has become an important tool in musculoskeletal radiology and neuroradiology.
Lameness (equine)
Computed tomography (CT) is an imaging modality that produces a 3-dimensional radiograph. A series of plain radiographs are taken in a spiral around the site of interest, and the individual 2-D radiographs are converted into a 3-D image by a computer. The image may be manipulated to view in different planes, such as cross-section, making it possible to see an injury from multiple perspectives and improving diagnostic capabilities when compared to plain radiographs. Like plain radiographs, CT is not as useful for soft tissue lesions when compared to boney lesions. However, CT requires general anesthesia, and is more costly and less available than plain radiographs, limiting its use in general practice. CT provides a large amount of data with exceptional speed, taking only seconds to minutes to complete. When compared to MRI, it is not only significantly faster (MRI takes 1–2 hours to produce an image), but also less expensive. Its combination of speed and imaging capabilities makes it beneficial for use prior to orthopedic surgery, especially in the case of complicated fractures, as it allows for visualization from all sides so that the surgeon may determine the best approach and method of correction prior to cutting. Upon completion of the CT, the horse may be rolled straight into the surgery suite for immediate surgical treatment. Advances in technology now also allows for a robotic scanner to rapidly image different parts the standing horse without the need for general anesthesia.