Scintigraphy
The RVC Equine Referral Hospital has a state of the art, purpose built high resolution scintigraphy system which is mainly used for bone phase scintigraphy (‘bone scanning’). Our system has been developed specifically for horses with its large high resolution rectangular gamma camera head and motion correction software. This system enables us to perform the examination efficiently and thoroughly thus optimising image quality.
Scintigraphy is particularly useful in horses as it allows structures to be visualised that would normally be difficult to evaluate due to the horse’s large size, for example the proximal limbs, back and pelvis. Scintigraphy is also useful in horses with lameness in multiple limbs.
While scintigraphy is mainly use in lameness diagnostics, the RVC Equine Referral Hospital has pioneered its application for the diagnosis of abdominal disorders such as abscesses and tumours in the horse, in addition to evaluating lung perfusion.
How are scintigraphy images acquired?
Scintigraphy is a diagnostic imaging technique used to image a tissue’s function and metabolic turnover. Molecules found exclusively in the tissue to be examined (for example, phosphonates for bone), are isolated and attached to a radioactive isotope (technetium-99m). The molecule is then injected into the animal and the emitted radiation is captured by external detectors (gamma cameras) to form two-dimensional images. This technique is also widely used in human diagnostic imaging.
Technetium has a half-life of 6 hours and, depending on how long it is left in the body before it is scanned, different phases can identified. Vasculature can be visualised immediately after injection and soft tissue can be seen 5-15 minutes post-injection, while the bone needs to be examined 2-3 hours after injection.
Focal areas of intense radiation in the images indicate increased uptake of the compound bound to technetium, meaning there is increased metabolic turnover. Increased uptake can often be due to tissue damage, for instance, micro-fractures, which may not be detected on radiographs. Micro-fractures can be a common problem in racehorses due to the mechanical stresses the bones are put under during training and racing, with the distal tibia being a common site for stress fractures.