Overview
ISO 22127:2019 - Dosimetry with radiophotoluminescent glass dosimeters (RPLDs) - specifies a standardized method for dose assessment when using RPLDs for dosimetry audit in MV X‑ray (megavoltage) external radiotherapy. The standard covers handling, irradiation, reading, conversion of readout to absorbed dose to water, required correction factors, performance requirements for the RPLD system (including the reader) and uncertainty evaluation. It explicitly excludes electron beams, stereotactic X‑ray beams and brachytherapy gamma‑ray dosimetry in this edition.
Key Topics and Requirements
- RPLD fundamentals: RPLDs are typically silver‑activated phosphate glass; RPL signal is proportional to absorbed dose, stable against fading, reusable after annealing, and allows repeatable readouts (intro notes uncertainties ~1–2% in certain conditions).
- Handling and preparation: rules for cleaning, annealing, pre‑heating and proper positioning of RPLD elements and casings.
- Measurement procedure: principles of measurement, objective measurement quantities, irradiation dose and effective centre of measurement, and reader positioning.
- Reading and data treatment: methods for determining RPL readings, mean raw data handling, background subtraction and reader stability compensation (reference RPLDs).
- Dose evaluation formulae: baseline formula to convert indicated values to absorbed dose to water, including definitions of calibration coefficient and individual dosimeter sensitivity correction.
- Correction factors: mandatory consideration of position dependence (reading tray), radiation quality (energy dependence), phantom material, and nonlinearity in response.
- System performance: technical, hardware/software, and documentation requirements for RPLD systems; detector and reader performance, repeatable reading ability, internal calibration glass, auxiliary equipment (annealing and pre‑heat) and failure detection.
- Uncertainty: guidance to assess measurement uncertainty in line with ISO/IEC Guide 98‑3 (GUM).
Practical Applications
- External dosimetry audits of MV X‑ray therapy beams performed by national metrology institutes, hospital physics QA teams, dosimetry audit providers and clinical medical physicists.
- Intercomparison exercises and conformity checks of linear accelerator output where passive, stable, and repeatable dosimeters are required.
- Use cases include routine external audit programs, quality assurance validation after machine repair or commissioning, and multi‑center audit studies.
Who Should Use This Standard
- Clinical medical physicists, QA engineers, dosimetry service providers, national standards bodies and manufacturers of RPLD systems/readers.
Related Standards
- Normative reference: ISO/IEC Guide 98‑3 (Uncertainty of measurement - GUM). ISO 22127:2019 is complementary to other radiotherapy dosimetry and QA standards used in clinical practice.
Keywords: ISO 22127:2019, RPLD, radiophotoluminescent glass dosimeters, dosimetry audit, MV X‑ray radiotherapy, absorbed dose to water, calibration, correction factors, reader performance, measurement uncertainty.