Overview
ISO 18310-1:2017 - Measurement and prediction of the ambient dose equivalent from patients receiving iodine‑131 administration after thyroid ablation (Part 1: During the hospitalization) - defines standardized methods to measure the ambient dose equivalent rate at a distance from inpatients treated with radioiodine (iodine‑131). The standard focuses on dosimetry using ionization chambers, calibration procedures, uncertainty estimation and quality control for hospital measurements while the patient remains admitted.
Key topics and technical requirements
- Scope and purpose: Establishes suitable procedures to quantify ambient dose equivalent H*(10) produced by patients after I‑131 therapy (post‑thyroid ablation) to support radiation protection of caregivers and the public.
- Measurement method: Direct measurement using an ionization chamber (or other suitable detectors) positioned at defined distances from the patient; includes guidance on detector alignment and positioning.
- Calibration methods: Describes two calibration approaches - the substitution method (compare readings with a reference chamber at the same point) and the reference radiation method (use a calibrated reference irradiation field). Specifies calibration environment (example: stabilize chamber, measure leakage current repeatedly).
- Environmental and geometric controls: Defines standard ambient conditions (20 °C, 101,325 Pa) and recommended calibration measurement conditions (e.g., ~23 °C ±2 °C, 50 % ±20 % RH). Requires beam size larger than detector sensitive volume by factor 1.5–2.
- Quality control and repeatability: Requires multiple pre‑ and post‑irradiation measurements, checks on leakage current, and repetition criteria if measurement differences exceed specified limits (e.g., ±0.3 % initial/final current or ±0.2 % atmospheric correction factor).
- Uncertainty estimation: Provides methods to construct an uncertainty budget, calculate combined standard uncertainty and expanded uncertainty for ambient dose equivalent measurements.
- Supporting models and annex: Includes a mathematical model for ionization chamber calibration and an informative experimental annex demonstrating measurement and prediction practice.
Practical applications and users
- Radiation protection officers and medical physicists performing in‑hospital dose assessments after I‑131 therapy.
- Nuclear medicine departments that need normative procedures for bedside or room‑based dose‑rate surveys.
- Accredited calibration laboratories calibrating ionization chambers for patient‑related gamma fields.
- Hospital safety and compliance teams implementing exposure control and discharge criteria based on measured dose rates.
Related standards
- ISO 4037 series (X and gamma reference radiation and calibration)
- ISO 4037‑3:1999 (conversion coefficients and calibration of area/personal dosemeters)
- ISO 29661 (reference radiation fields)
- ISO/IEC Guide 99 (VIM - metrology vocabulary)
Keywords: ISO 18310-1:2017, ambient dose equivalent, iodine‑131, ionization chamber, calibration, uncertainty estimation, thyroid ablation, radiological protection.
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