Dosimetry Laboratory

On this page

1. Introduction
2. Calibration services
3. Dosimetry Audit services
4. Education and Training activities
5. Research and Development activities (Coordinated Research Projects)

Introduction

The use of radiation in medicine is continuously evolving, due to clinical and technological developments. New imaging and therapy modalities require accurate dosimetry and comprehensive quality assurance (QA). The IAEA supports its Member States in enhancing their capabilities to implement radiation imaging and treatment modalities safely and effectively through optimized dosimetry and medical physics practice.     Aligned with this mandate, the IAEA Dosimetry Laboratory (DOL) of the Dosimetry and Medical Radiation Physics (DMRP) section of the Division of Human Health (NAHU), plays a key role in providing services and establishing and disseminating best practices in radiation metrology and dosimetry auditing, linked to the international measurement system.

The IAEA DOL was established in 1961 and is located at the IAEA’s Laboratories, Seibersdorf, near Vienna.   It is equipped with a range of irradiators, dosimetry systems and necessary auxiliary equipment, which include a linear accelerator, 2 Co-60 therapy machines, a gamma beam irradiator (with a Cs-137 and a Co-60 source) for radiation protection calibrations, a calibration X ray unit covering mammography, diagnostic and therapy radiation qualities, and a high dose rate brachytherapy afterloader which can be operated with either a Co-60 or an Ir-192 source.  Diverse ionization chambers and electrometers are used as reference standards for dosimetry.   Other dosimetry systems used include Thermo Luminescence Dosimeters (TLD), Optically Stimulated Luminescence Dosimeters (OSLD), Radio Photo Luminescence Dosimeters (RPLD) and film dosimeters.

The IAEA/WHO Network of Secondary Standard Dosimetry Laboratories was established in 1976, with the DOL as the central laboratory of the Network. The objective of this network is to ensure international consistency in dosimetry at end-user level, in accordance with the International Committee for Weights and Measures (CIPM) and International Mutual Recognition Arrangement (MRA), signed by the Agency in 1999.  National standard dosimetry laboratories in Member States send their reference dosimeters for calibration to DOL, to ensure traceability. Under exceptional circumstances, the IAEA DOL also supports end-users in the Member States that do not have a national SSDL by providing calibration service.

Dosimetry audits provide an independent verification of the dose delivered by radiotherapy treatment machines, thus reducing the risk of mistreating cancer patients and preventing radiation accidents. Independent dosimetry audits are required by the IAEA International Basic Safety Standards No. GSR Part 3. In response to requests by Member States, the dosimetry audit services started in 1969 as a joint project with the World Health Organization-WHO and Pan American Health Organization-PAHO.  Many discrepancies in radiotherapy dosimetry have been discovered and rectified, resulting in better accuracy in clinical dosimetry leading to quality in cancer care. 

Furthermore, the IAEA DOL plays a key role in research and development and in the education of medical physicists and radiation metrologists that enhances the scientific and technical capacity in radiation dosimetry worldwide. One of the mechanisms for IAEA DOL to disseminate knowledge through training courses and identify research needs through Co-ordinated Research Projects. The IAEA DOL activities are coordinated with other national dosimetry laboratories, professional societies, organizations and stakeholders who are active in this area, such as the International Consultative Committee for Standards of Ionizing Radiations (International Bureau of Weights and Measures), regional metrology organizations and professional societies in medical physics and radiation dosimetry.

The IAEA DOL is operated following a peer-reviewed quality management system based on ISO/IEC 17025:2017.

All services of the  IAEA DOL are available cost-free to the Member States. 

Calibration services

Reference dosimetry is carried out using a reference standard, for example, an ionization chamber connected to an electrometer. The reference standards are traceable to the International Measurements System (IMS). The standards can be either calibrated at a Primary Standards Dosimetry Laboratory (PSDL), a Secondary Standards Dosimetry Laboratory (SSDL), such as the IAEA DOL.

In radiation metrology, calibrations are performed by using a range of equipment, methods, and techniques, depending on the types of instruments that must be calibrated, as well as on the conditions under which the instruments are likely to be used. The calibration is intended to determine a calibration factor appropriate to the routine application of the dosimeter. The calibration factor of the dosimeter is only valid for the reference conditions and radiation beam qualities in which it was calibrated. Any difference from these conditions must be considered in the clinic such as geometry of measurements, radiation quality temperature and pressure, humidity, ion recombination and polarity. 

More information about the IAEA/WHO Network, and the services provided by the IAEA DOL may be found on the dedicated webpage. 

Audit services

It is the responsibility of the clinical facility to ensure that all radiation beams are properly calibrated prior to the first treatment and that the output is monitored for stability over the lifetime of the device.  Independent external dosimetry audits play a key role in ensuring this and confirmation of calibration accuracy.  Dosimetry audits promotes a safety culture in radiotherapy departments, which is especially crucial as radiotherapy techniques are becoming more and more complex and less intuitive.  Dosimetry audits have been proven to be effective in identifying problems in clinical dosimetry.   The results of the IAEA/WHO postal dosimetry audits are confidential in nature and are treated with the sole intention to improve the accuracy and consistency of clinical dosimetry and not for regulatory requirements.  The IAEA DOL dosimetry audit services covers a wide spectrum of users including radiotherapy hospitals, SSDLs and Dosimetry Audit Network (DAN) members.

Dosimetry audits to radiotherapy centres

The IAEA DOL audit service for hospitals is organized in 9 irradiation batches every year and is based on passive solid-state dosimeters that are sent through postal service to the participating institutes. Currently, RPLDs are being used, superseding TLDs till 2017.  Medical Physicists at the participating institutions are provided with instructions to irradiate the dosimeters in the machine-specific reference conditions using special holders to a dose of 2 Gy in water. After the irradiation, the dosimeters are sent back to the IAEA DOL for analysis. Once analysed, a certificate with the audit results is issued. Any deviation is usually followed-up by an independent Radiotherapy Medical Physicist through direct communication with audit participants. The service is available for Co-60 gamma, high energy photon and electron beams.

Dosimetry audits to SSDLs

The dosimetry audit services were expanded in 1981 to monitor the consistency of dosimetry practices at SSDLs, which benefit from both radiation therapy level (Co-60, high energy photons and electrons) and radiation protection level (Cs-137) audits service once per year. Radiotherapy level audits are performed using the same dosimetry system as for hospitals (RPLDs) and follow the same approach, however, RP level audits utilize OSLDs irradiated in air with 5 mGy air-kerma.

Dosimetry audits to DAN

The DAN members can benefit from verifying their measurement capabilities through reference and blind irradiations provided by the DOL. These irradiations are performed in Co-60, high-energy photons, and electrons.   Besides irradiations in reference conditions, non-reference irradiations can be provided upon request. This service brings together different auditing groups and laboratories worldwide. More information about the DAN services, may be found on the dedicated upcoming webpage

Comprehensive audits of radiotherapy practices

An independent external clinical audit within a quality management system is a useful tool for quality improvement in radiotherapy.  In response to the requests from Member States, the IAEA has developed and published a series of methodologies for comprehensive hospital audits in diagnostic radiology (QUAADRIL), radiotherapy (QUATRO) and nuclear medicine (QUANUM).  Independent clinical audits of the programme of quality assurance for medical exposures are also requirement of the IAEA International Basic Safety Standard.

Quality Assurance Team for Radiation Oncology (QUATRO) audit is performed by a multidisciplinary team of experts comprised of a radiation oncologist, a medical physicist, and a radiotherapy technologist, who spend 3-5 days onsite at the facility. The auditors follow a well-designed protocol, and they have all received additional training in auditing procedures. Through the application of 37 clinical process, related checklists, and 5 questionnaires related to radiotherapy practice, the comprehensive audit, reviews and evaluates the quality of all elements involved in radiation therapy. A preliminary assessment of the programme is provided to the institution at the conclusion of the visit followed sometime later by a detailed written confidential report with recommendations for quality improvement. Adoption of the auditors’ recommendations is purely at the discretion of the institution.   IAEA DOL supports QUATRO by providing equipment and ensuring traceability of dosimetry performed during the QUATRO audit. 

Education and Training activities

Lack of skilled human resources in the field of dosimetry is a common challenge in many Member States. The IAEA DOL and its human and technical resources has successfully implemented several activities to fill the gap and support Member States in enhancing their capacity to implement radiation imaging and treatment modalities safely and effectively, by supporting education and training activities in dosimetry calibrations, dosimetry auditing, quality management, as well as physics aspects of quality assurance and quality control of linear accelerators.  

The training and exchange of scientific knowledge is offered through various mechanisms such as internships, fellowships and scientific visits. All IAEA DOL trainees are introduced to quality management system for calibration and testing laboratories based on the ISO/IEC 17025 standard.

Training in calibrations include wide range of activities covering radiotherapy, radiation protection and diagnostic radiology level   calibrations and comparisons (e.g. IAEA TRS 398 and IAEA TRS 483, IAEA SRS 16, IAEA TRS 457), including establishment of radiation qualities, calibration protocols and procedures, assessment of the uncertainty budget and quality control of dosimetry equipment

For dosimetry auditing, the training covers characterisation of dosimetry systems based on TLDs, RPLDs and OSLDs, calibration and maintenance of the dosimetry systems, determination of absorbed dose or air kerma from dosimeter readings, analysis of uncertainties and operation of a postal dose audit service. 

Linear accelerator-based training activities are usually addressed to clinical medical physicists and cover all aspects of dosimetry and quality assurance

Research and Development activities (Coordinated Research Projects)

Coordinated Research Projects (CRPs) are designed to encourage the acquisition and dissemination of new knowledge in the field of dosimetry and medical physics. Support to research work is provided by developing new devices, procedures and methodologies that can be used for quality assurance and dosimetry. CRPs involving dosimetry aspects are usually supported by DOL. Additionally, DOL is actively involved in organizing and running CRPs in the areas of its expertise. For example, many Member States are facing multiple challenges in designing and running effective dosimetry audits, including audit design, appropriate methodologies, characterization of dosimetry systems, phantom design, database architecture and maintenance, among others. In this scenario, to extend the availability of dosimetry audits to as many radiotherapy centres as possible throughout the world, the IAEA supported the development of methodologies and helped establish several national audit networks.

The following CRPs have been conducted by the IAEA over the last decades to assist in developing national programmes for remote dosimetry audits:  

• Development of a Quality Assurance Programme for Radiation Therapy Dosimetry in Developing Countries
• Development of a TLD-based Quality Audit Programme for Radiotherapy Dosimetry in Non-Reference Conditions 
• Development of Quality Audits for Radiotherapy Dosimetry for Complex Treatment Techniques  
• Development of Quality Audits for Advanced Technology in Radiotherapy Dose Delivery  

The overall radiotherapy dosimetry audit approach established and developed throughout the CRPs is based on a process of increasing the complexity of audit steps, from simple to advanced techniques, so that experience of previous steps is used to inform development, implementation and analysis of results for subsequent audit steps. Altogether, 11 audit methodologies were developed, tested and implemented internationally which explains the wide timeframe covered in the DOL history of research in dosimetry audits. Currently, a new CRP is in progress which aims to develop a methodology for brachytherapy audits.