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Dosimetry and Medical Radiation Physics

The IAEA/WHO SSDL Network

The IAEA/WHO Network of Secondary Standards Dosimetry Laboratories (SSDL Network) was established in 1976 as a joint project between the IAEA and the World Health Organization (WHO). At present, it includes
80 laboratories and six (6) SSDL national organizations in 67 Member States
, of which over half are developing countries.

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The SSDL network also includes 15 affiliated members (Primary Standard Dosimetry Laboratories, PSDLs) and 5 collaborating organizations; these supply support to the Network.

The Secretariat functions of the network are shared between IAEA and WHO, the IAEA being responsible for the technical developments of the member laboratories. The Head of the Dosimetry and Medical Radiation Physics Section functions as a secretary of the SSDL Network, and is supported in his functions by the SSDL Project Officer.

The SSDL project has the responsibility to verify that the services provided by the national laboratories follow internationally accepted metrological standards, including also the traceability for radiation protection instruments. IAEA's support is accomplished first with the transmission of calibration factors for ionization chambers from the BIPM or PSDLs through the IAEA's Dosimetry Laboratory. Interested SSDLs should download the calibration form, fill it out and send it to the Dosimetry and Medical Radiation Physics Section. SSDLs whose instruments were calibrated at the IAEA's Dosimetry Laboratory can also download the relevant appendices of calibration certificates issued by the IAEA (Appendix Brachytherapy calibration, Appendix external radiotherapy level calibration, Appendix Mammography calibration, Appendix radiation protection level calibration) As a second step, follow-up programmes and dose quality audits are implemented for the SSDLs to guarantee that the standards transmitted to users in the Member States are kept within the levels required by the International Metrology System. For more than 15 years a postal TLD programme has monitored the performance of the SSDLs in the therapy dose range. A comparison of ionization chamber calibration coefficients is offered for SSDLs. Interested SSDLs should download the comparison procedure and contact the SSDL Officer for scheduling.

Membership in the network is open to laboratories designated by their national competent authority. Guidelines to Member States on the designation of SSDLs and the criteria to be met by a national SSDL to be accepted in the IAEA are available through the network Secretariat in the Dosimetry and Medical Radiation Physics Section.

One of the principal goals of the SSDL network is to guarantee that the dose delivered to patients undergoing radiotherapy treatment in the Member States is kept within internationally accepted levels. During the last years the trend towards the implementation of quality assurance (QA) procedures in radiotherapy has been based on the criticality of biological response to radiation dose, as the probabilities of tumour control and normal tissue complication are closely related to a correct patient dosimetry. Recent activities of the IAEA towards the SSDL network have not only been addressed to establish metrological institutions of high quality, but also to emphasize the support of the SSDLs to QA programmes for radiotherapy. This is accomplished not only by insuring that the calibrations of instruments provided by SSDLs are correct, but also by promoting the contribution of SSDLs to perform dosimetry quality audits in therapy centers, and if needed, to help perform calibrations of radiotherapy equipment in hospitals. Depending on the equipment and the staff available at the laboratory, and sometimes depending also on the functional organization of the SSDL, these activities vary between different countries.

Staff from the SSDLs of the IAEA/WHO network are accepted for training in the IAEA's Dosimetry Laboratory upon request from the SSDL using the standard procedures of communication with the IAEA.

The Dosimetry and Medical Radiation Physics Section publishes periodically a SSDL Newsletter which is distributed among the members of the SSDL network and to the scientific community.