What is a Bone Scan?

Updated: Mar 14, 2023

Author: Katherine Murray BVMedSci BVMBVS CertAVP MRCVS

Nuclear scintigraphy, or “bone scan”, is a diagnostic technique most often utilized in the investigation of equine lameness or poor performance. At Donnington Grove, we have over 30 years of experience and expertise in the acquisition and interpretation of scintigraphic images.

How do we do it?

In preparation for a bone scan the horse is usually exercised and kept warm including wrapping the legs and rugging up. This helps to improve blood flow around the body before a radioactive isotope called Technicium 99m is administered intravenously. This radioactive isotope acts as a marker for bone so when the horse is imaged the outline of the skeleton will be visible.

Two hours after the injection the radioactive isotope will have made its way into the horses' bones which means the scanning can commence! The horse is taken into the bone scan room and sedated so that they stand still enough for the scans. They stand in front of the 'gamma camera' which picks up the radioactive isotope and creates an image. Each image takes 90 seconds to acquire and the horse must stay extremely still. It takes approximately 2 hours to acquire all of the images, this time varies depending on how well the horse stands still and how often they urinate. The technicium is expelled in the urine, so if the horse has a full bladder they may need to be returned to the stable and allowed to urinate before the images of the pelvis can be acquired.

What does it tell us?

The radioactive isotope attaches to cells with high turnover, so where there are areas of disease such as arthritis or injuries such as fractures there will be a higher concentration of radioactive isotope. The images appear on the screen as a series of dots. So in problem areas the dots are more dense so appear brighter on the image, these are known as 'hot spots

Once all of the images have been acquired the radioactive horse goes back to the same stable and must stay here until it is no longer passing high levels of radioactive isotope in its urine. All bedding from the stable has to be disposed of very carefully in clinical waste. The following day the 'hot spot' areas can be investigated with further imaging such as radiographs and ultrasound.

Pros	Cons
Whole body imaging Good for multiple areas of interest Useful for deep boney structures such as the neck, back and pelvis which can be difficult to x-ray. Useful in horses which are needle shy and can't be nerve blocked safely Good for stress fractures (a common injury in racing Thoroughbreds)	'Bone scan' - not much use for soft tissue injuries! Expensive Usually requires further imaging of 'hot spots' once identified Technicium (radioactive dye) comes with risks towards hospital staff. Not as useful for chronic lameness.