Overview
ISO 16645:2016 - Radiological protection - Medical electron accelerators - Requirements and recommendations for shielding design and evaluation - provides guidance for designing and evaluating shielding for medical electron linear accelerators (LINACs) with nominal beam energies from 4 MV to 30 MV. The standard covers conventional LINACs and particular installations such as robotic-arm systems, helical intensity‑modulated radiotherapy (helical IMRT) and dedicated intra‑operative radiotherapy (IORT) electron devices. Cyclotrons and synchrotrons for hadrontherapy are excluded.
ISO 16645:2016 is a practical reference for radiological protection, shielding design goals, calculation methods, measurement verification, and stakeholder roles.
Key topics and technical requirements
- Shielding design goals and assumptions: Defines protection objectives, occupancy categories and design criteria used for room and barrier specifications.
- Radiation fields around LINACs: Describes X‑ray primary/secondary/tertiary components, neutron production for high‑energy beams, and capture gamma contributions.
- Shielding materials and transmission values: Provides guidance on material selection and where to find tenth‑value layer (TVL) data (see Annex A).
- Calculation methods: Formalism for primary and secondary barrier calculations, multi‑layer barriers, and worked examples (Annex C).
- Doors, mazes and ducts: Design and calculation procedures for standard mazes, two‑leg mazes, direct‑shielded doors, HVAC ducts and the impact on dose outside the room.
- Special device configurations: Additional recommendations for robotic-arm accelerators, helical IMRT and IORT electron units.
- Skyshine and groundshine: Considerations for scattered radiation that reaches on‑site and off‑site locations via the atmosphere or ground.
- Measurement and verification: Procedures for radiological monitoring, experimental shielding evaluation and acceptance measurements.
- Roles and interactions: Responsibilities of manufacturers, shielding material vendors, architects/contractors, licensees and radiation protection officers/qualified experts.
- Safety systems: Signage, interlocks and operational controls for radiological protection.
Applications and users
ISO 16645:2016 is intended for:
- Medical physicists and radiation protection officers
- Hospital engineers and architects designing LINAC vaults
- Shielding consultants and qualified experts performing shielding calculations
- Accelerator manufacturers and shielding material suppliers
- Regulatory bodies and licensing authorities reviewing shielding submissions
Practical applications include designing radiation therapy treatment rooms, specifying barrier thicknesses, sizing mazes and doors, evaluating HVAC duct penetration shielding, and performing final shielding verification measurements.
Related standards and guidance
Users should apply ISO 16645:2016 alongside applicable national radiation protection regulations and international guidance (e.g., IAEA and IEC publications) and local licensing requirements to ensure compliance and optimized shielding design.