Magnetic resonance imaging (MRI) is an imaging technique that uses magnetic fields to create various types of cross-sectional and three-dimensional images. While commonly used by physicians, MRI has only been used in equine clinical cases for the past decade and has come into widespread use just within the past five years. This modality provides superior soft tissue and bone detail, allows detection of abnormalities in an earlier state of disease, and is considered the gold standard in many cases.
Magnetic field strength is measured in Tesla (T). The strength of the magnetic field varies between types of magnets but is typically between 0.3 T and 1.5 T for most magnets currently in routine equine clinical use. Increased magnetic field strength means that examinations can be obtained with higher resolution in a shorter time. The strong magnetic field causes the molecules in the body to align slightly differently than they do while under only the influence of the earth’s magnetic field. This influence allows us to manipulate the molecules using targeted electromagnetic gradients and radiofrequency pulses in various ways to gain more information about the tissues.
A typical MRI examination produces hundreds of individual images to be reviewed and usually takes between one and two hours to complete. Specific sequences are optimized to highlight regions of inflammation, changes in anatomical structure, or areas of chronic damage.
Magnetic resonance imaging is often used when other imaging modalities such as radiography, ultrasonography, or nuclear scintigraphy have failed to provide a specific diagnosis. These failures may be due to the fact that t