AAPM Task Group 108: PET and PET/CT shielding requirements

Area of Science:

• Medical Physics
• Radiological Sciences
• Nuclear Medicine Technology

Background:

• Positron emission tomography (PET) and PET/CT facilities face unique radiation shielding challenges.
• The 0.511 MeV annihilation photons from positron decay necessitate significant shielding in walls, floors, and ceilings.
• Patients act as the primary radiation source post-radiopharmaceutical administration, requiring consideration of exposure over time.

Purpose of the Study:

• To present methods for estimating radiation shielding requirements for PET and PET/CT facilities.
• To provide data and calculations for effective shielding design.
• To ensure radiation safety standards are met cost-effectively.

Main Methods:

• Summarizing physical properties of common PET radionuclides, focusing on fluorine-18.
• Reviewing typical PET imaging protocols to estimate patient exposure rates, accounting for self-attenuation and decay.
• Performing barrier calculations for controlled and uncontrolled areas, including adjacent rooms with scintillation cameras.

Main Results:

• Estimated transmission factors for lead, steel, and concrete at 0.511 MeV are provided in tables and graphs.
• Examples of barrier calculations demonstrate shielding needs for various facility areas.
• Meeting regulatory limits for uncontrolled areas can be costly, highlighting the need for careful planning.

Conclusions:

• Effective shielding design for PET/PET-CT facilities requires collaboration between vendors, architects, and medical physicists.
• Careful planning is essential for a cost-effective design that maintains radiation safety.
• The methods presented aid in optimizing shielding to meet stringent regulatory requirements.