Biological and imaging characteristics and radiation dose rates associated with the use of technetium-99m-labelled imidodiphosphate in the horse.

This research examines the biological and imaging attributes, as well as radiation dose rates linked to the use of technetium-99m-labelled imidodiphosphate (Tc99m-IDP) in horses. The study noted clearance rates of the radiopharmaceutical from the horse blood and traced levels of radioactivity concentration in the urine and bone-to-soft tissue, to suggest that 24 hours is an adequate radioisolation time for adult horses given this radiopharmaceutical.

Key Findings

The authors made several measurements and computations in horses that were administered Tc99m-IDP. These measurements were aimed at understanding how the radiopharmaceutical behaves in a horse’s body, and how long it takes to be cleared from the system. The key findings of the research include:

• Clearance half-time of Tc99m-IDP from the horse’s blood was measured to be approximately 29.6 +/- 2.3 minutes within a 95.5% confidence limit. This means that roughly half of the administered Tc99m-IDP was removed from the blood system in that span of time.
• Four hours after administering the dose, only about 3.9 +/- 0.8% of the administered dose was observed to be circulating in the whole-blood volume.
• The Tc99m-IDP radioactivity held within the plasma fraction of the whole blood was found to be approximately 85.3 +/- 1.6% at four hours post injection.
• Approximately 45 +/- 16% of the administered dose was found to have been expelled through the urine 8 hours post the dose administration.
• The mean effective half-time of the urine activity concentration was measured to be around 1.1 +/- 0.3 hours. This means it took roughly 1.1 hours for the concentration of Tc99m-IDP in the horse’s urine to reduce by half.
• The bone-to-soft tissue activities’ ratio increased with time post the injection, suggesting an increased localization of the Tc99m-IDP in the bone over time.

Radioisolation Time

Coupling the above findings with an analysis of urinary radioactivity concentration measurements and radiation dose rate measurements immediately post the administration of the dose, the researchers determined that 24 hours is an adequate radioisolation time for horses administered 3.7 GBq (100 mCi) of Tc99m-IDP.

This time denotes the period during which the horse should be isolated to prevent unnecessary radiation exposure to humans or other animals. After this time, most of the radioactive substance has been metabolized or excreted, bringing radiation levels within safe limits.

Overall, the study provides crucial evidence on the use of Tc99m-IDP in diagnostic imaging in horses, affirming its efficiency and holding significant implications for its safe use.