Air activation produced by high-energy medical accelerators

Area of Science:

• Medical Physics
• Radiation Safety
• Nuclear Medicine

Background:

• Medical accelerators are widely used in radiation therapy.
• Accelerator operation can potentially activate air, producing radioactive isotopes like oxygen-15 (15O) and nitrogen-13 (13N).
• Understanding the levels of these isotopes is crucial for ensuring the safety of staff and patients in treatment rooms.

Purpose of the Study:

• To directly measure the activity of 15O and 13N in air following medical accelerator operation.
• To assess the radiological safety of treatment rooms by comparing measured concentrations to maximum permissible limits.
• To investigate and compare different calibration techniques for air radiation detectors.

Main Methods:

• Direct measurement of 15O and 13N activity per unit volume of air.
• Operation of 25-MeV and 45-MeV medical accelerators to maximize air activation.
• Comparison of measured air concentrations with established maximum permissible concentrations.
• Evaluation of three distinct air detector calibration methodologies.

Main Results:

• Measured air activity levels for 15O and 13N were found to be 1% or less of the maximum permissible concentration.
• These low levels were observed immediately after accelerator shutdown.
• The study successfully investigated three different air detector calibration techniques.

Conclusions:

• Operation of 25-MeV and 45-MeV medical accelerators results in negligible and safe levels of airborne 15O and 13N.
• The measured concentrations pose no significant radiological risk in treatment rooms.
• Effective calibration techniques for air monitoring detectors are essential for accurate safety assessments.