Dosimetry and Medical Radiation Physics (DMRP)

Calibration of Measurement Standards

Measurement standards of Member States used for radiotherapy (including brachytherapy), mammography and radiation protection (including environmental) dosimetry are calibrated, free of charge, at the IAEA’s Dosimetry Laboratory. Inquiries for scheduling and turn-around time should be addressed to the SSDL Officer (Dosimetry and Medical Radiation Physics Section) by letter, fax or e-mail. Interested SSDLs should fill in a calibration form and send it to the SSDL officer. The IAEA calibration services are based on its Calibration and Measurement Capabilities published in Appendix C of the BIPM key Comparison Database. After arrangements for calibration are made, the instruments can be shipped to the SSDL Officer. Care must be taken for packaging the instrument to avoid damage during their transport which should be covered by insurance. A calibration certificate is issued for each calibration.

Therapy level

Reference class ionization chambers and electrometers are calibrated at the IAEA’s Dosimetry Laboratory by the substitution method using the IAEA’s reference standards calibrated at BIPM. Calibrations are either made for a system composed of an ionization chamber plus an electrometer or for an ionization chamber alone.

Well type ionization chambers for low dose rate brachytherapy

Well type ionization chambers are calibrated in terms of reference air kerma. Calibrations are made for low dose rate brachytherapy sources using the IAEA’s standard (caesium-137) traceable to NIST.

Gamma ray calibrations

Ionization chambers are calibrated in terms of air kerma and absorbed dose to water in a collimated cobalt-60 gamma ray beam. For air kerma calibration, the chamber is positioned with its build-up cap at 1 meter from the source in a field size of 10 cm X 10 cm.

For in water calibrations, the chamber is protected with a PMMA sleeve and positioned in a water phantom at 1 meter from the source and at a depth of 5 g/cm2. Calibrations in terns of absorbed dose to water are performed for SSDLs and hospitals (in countries with no SSDL) that have implemented a dosimetry protocol based on absorbed dose to water standards.

X-ray calibration

Ionization chambers are calibrated in terms of air kerma at eight beam qualities (recommended by CCEMRI). The characteristics of the ionization chamber submitted for calibration should be taken into account in the selection of X-ray beam qualities. The chamber is positioned, without its build-up cap, at 1 meter from the focus of the X-ray tube for medium energy X-rays and at 0.5 m for the low energy X-rays.

PROTECTION LEVEL

Reference class ionization chambers and electrometers are calibrated using the IAEA’s reference standards calibrated at BIPM and PTB. Calibrations are either made for a system composed of an ionization chamber plus an electrometer or for an ionization chamber alone.

Gamma ray calibrations

Ionization chambers are calibrated in terms of air kerma and ambient dose equivalent for cobalt-60 and caesium-137 gamma ray beams. The chamber is positioned at 3 meters from the source.

X-ray calibrations

Ionization chambers are calibrated in terms of air kerma at nine ISO-4037 X-ray beam qualities. The chamber is positioned at 3 meters from the X-ray tube focus.

Reference & blind irradiations to dosimeters

The IAEA provides reference irradiations needed for the calibration of individual monitoring systems (TLDs or films) to SSDLs and national dosimetry monitoring services (in countries with no SSDL). Blind irradiations can also be provided to test the calibration of individual monitoring systems. Interested SSDLs should fill in the irradiation form and send it to the SSDL Officer.