Spatial and temporal radiation exposure during equine bone scintigraphy: Implications for occupational safety and post-scintigraphy isolation.

BACKGROUND

Bone scintigraphy is a valuable diagnostic modality in equine orthopaedics, but it is associated with occupational radiation exposure and regulatory requirements for post-procedural isolation.

OBJECTIVES

To quantify radiation dose rates emitted from horses undergoing bone scintigraphy, to evaluate the effects of distance (spatial) and time (temporal) on radiation exposure, and to derive evidence-based recommendations for post-scintigraphy isolation periods.

STUDY

DESIGN

Prospective, cross-sectional study.

METHODS

Twenty warmblood horses underwent musculoskeletal scintigraphy following intravenous administration of 99 mTc-methylene diphosphonate (approximately 10 MBq/kg). Radiation dose rates (μSv/h) were measured at the head, kidney, and pelvic regions at distances of 5, 30, and 100 cm from the skin. Measurements were recorded from 5 min up to 72 h post-injection.

RESULTS

At 5 min post-injection and 5 cm distance, the kidney region exhibited dose rates 38% higher than the head (p = 0.001; 95% CI = 39.1-101.8), whereas the pelvic region showed significantly lower values (28.2%-55.5% reduction; p < 0.05). Increasing the distance from 5 cm to 30 cm and 100 cm reduced radiation exposure by 65%-82%, representing a greater protective effect than time decay alone (p < 0.05). Across all anatomical regions, dose rates at 5 cm decreased to ≤45 μSv/h by 6 h and to ≤7.5 μSv/h by 18 h post-injection.

MAIN LIMITATIONS: Potential effects of pathological tracer uptake and limited representation of older horses requiring higher radiotracer doses.

CONCLUSIONS

Maintaining a minimum distance of 30 cm from horses undergoing bone scintigraphy substantially reduces occupational radiation exposure. The post-scintigraphy isolation periods can be shortened to 6 h under German regulations and to approximately 18 h to meet international standards.