Monte Carlo evaluation of occupational exposures in equine radiology procedures.

Overview

• This study uses Monte Carlo simulations to evaluate radiation exposure risks to workers assisting in equine X-ray procedures.
• It investigates how protective equipment and distancing impact occupational radiation doses during horse diagnostic imaging.

Introduction and Background

• Portable X-ray machines provide essential diagnostic imaging for horses but involve exposure to ionizing radiation.
• Workers often physically restrain horses during imaging, increasing their radiation exposure risk.
• Assessing occupational radiation doses helps to understand health risks and improve safety measures.
• Monte Carlo simulations provide a computational approach to estimate radiation dose distribution in complex scenarios.

Methods and Simulation Setup

• The research utilizes the Monte Carlo N-Particle 6.2 (MCNP6.2) simulation code to model radiation transport.
• Virtual anthropomorphic phantoms representing workers are used: FASH3 for female and MASH3 for male models.
• A realistic virtual horse phantom was created by converting a commercially available 3D horse model into a voxel-based representation, allowing accurate radiation interaction modeling.
• X-ray beam spectra were generated using the SpekCalc program with parameters:
  • Tube voltages: 90 kV and 100 kV
  • Anode angle: 20°
  • Filtration: 2.7 mm Aluminum
  • Field of view: 43 × 35 cm
• Two scenarios were simulated:
  • Scenario 1: Workers without personal protective equipment (PPE)
  • Scenario 2: Workers wearing PPE (lead apron, thyroid protector, lead glasses) and maintaining increased distance from the X-ray source/horses

Key Radiation Dose Metrics

• Conversion Coefficients were calculated:
  • CC[H]: Equivalent Dose coefficients for specific organs/tissues
  • CC[E]: Effective Dose coefficients estimating overall health risk
• Doses were normalized by Air Kerma, a measure of the kinetic energy transferred from photons to air, serving as a reference for exposure.

Results

• Without protection:
  • The thyroid was the most irradiated organ for the female phantom (FASH3).
  • The breasts received the highest dose for the male phantom (MASH3).
  • The assistant (person physically restraining the horse) experienced up to 28 times higher effective dose (CC[E]) than the X-ray tube operator.
• With PPE and increased distance:
  • Equivalent doses (CC[H]) for assistants were reduced by at least 99%.
  • Doses for tube operators were reduced by at least 97%.
  • This demonstrates the efficacy of combined protective measures in significantly lowering occupational radiation exposure.

Conclusions and Implications

• The study quantitatively demonstrates the high radiation exposure risk to workers, especially assistants, during equine radiology without protection.
• Monte Carlo simulations successfully model complex interactions between radiation, workers, and the animal patient.
• The results emphasize the critical importance of using personal protective equipment and maintaining distance to minimize health risks.
• Findings can inform safety protocols and training for veterinary radiology staff.
• Overall, adopting PPE and optimized working positions can reduce occupational radiation dose by over 95%, promoting safer working conditions.