Quantitative evaluation of bone scintigraphy of the spinous processes of the equine thoracic spine at different times after administering ⁹⁹mTc-hydroxymethylene-diphosphonate.

This research article investigates the optimal time to get the best quality scintigraphic images of a horse’s thoracic spine following the injection of a particular radionuclide. It suggests that imaging should ideally be carried out four to six hours after the administration of the radionuclide.

Objective of the Research

• The study’s primary goal was to find the best time to take scintigraphic images of the equine thoracic spine after injecting (99m)Tc-HDP (hydroxymethylene-diphosphonate). This radionuclide helps visualize changes at the cellular level in the equine thoracic spine.
• It aimed to achieve images with superior contrast and sufficient count rates, which are crucial for detecting lesions and other issues in the thoracic spine and surrounding soft tissue.

Methodology

• Twenty-one horses underwent scintigraphic examinations of their thoracic spines.
• These images were captured at three different intervals (two, four, and six hours) after injection of the radionuclide.
• Eight regions of interest (ROI) were identified within the images – four within the spine’s processes and four in adjacent soft tissue.
• The researchers then determined and compared the bone and soft tissue uptake, and the bone-to-soft tissue ratio at various time points.

Findings

• The total count rates, or level of radioactivity, decreased over time but remained high (at least 150,000 counts per image).
• The bone-to-soft tissue ratio was marginally higher in images acquired six hours after the radionuclide injection compared to images taken after two and four hours. This improvement was statistically significant (P<0.01), suggesting that later imaging provided better contrast and thus, better quality images.

Recommendations and Conclusions

• Based on the study results, the researchers recommend conducting the scintigraphic examination of the equine thoracic spine four to six hours following the injection of (99m)Tc-HDP.
• However, they acknowledge the need for additional studies, particularly to understand how delayed imaging compares to images taken after just three hours. They want to determine if this affects the ability to detect lesions in different parts of the thoracic spine and surrounding soft tissue.