Nuclear scintigraphy
Equine scintigraphy (bone scan)
Nuclear scintigraphy (bone scan) is a diagnostic imaging technique, which uses a radioactive isotope to detect areas in the skeleton, where active modelling occurs. These areas are recognised as ‘hot spots’ on the image. Scintigraphy is mostly used as a part of lameness investigation, but it can also provide valuable information for dental disorders, respiratory and other medical problems. It is paramount to select the appropriate cases, in which scintigraphy can potentially be useful; scintigraphy should not be used as a screening procedure. Scintigraphy is always performed after a thorough clinical examination and sometimes after some other diagnostic procedures, which failed to explain the lameness. It can be very useful to detect injuries at an early stage, such as stress fractures, which mostly occur in Thoroughbred racehorses. In sports horses, amongst others, scintigraphy can help to diagnose lesions in the foot, sacroiliac regions and back. Besides detecting lesions not identifiable by other imaging techniques, scintigraphy can also help to establish the clinical significance of lesions detected by radiography, ultrasound or MRI.
Procedure
Horses are usually admitted on the day prior to the planned scintigraphic examination. It is important that horses are exercised prior to admission to maintain good blood flow in the limbs, which will contribute to good quality images. On the day of the scan, a catheter is placed in one of the jugular veins, and the isotope is injected in the morning. It takes approximately 2 ½ hours to achieve good distribution of the isotope in the bones, therefore the actual scanning is performed in the early afternoon. Horses are sedated for the scan and usually tolerate the procedure very well. Depending on how big part of the horse has to be scanned, and also, how the horse behaves, the examination lasts between 1 and 3 hours. Due to radiation safety and local regulations, horses are kept in isolation for 36 hours after the injection of the isotope, which means that further investigation can be performed 2 days after the scan. This is also the earliest time, when the horse can leave the hospital.