An IAEA radiation metrologist at the Dosimetry Laboratory setting up for calibrating an ionization chamber for external beam radiotherapy. (Photo: D.Calma/IAEA).
Radiation therapy is one of the most effective treatments for many kinds of cancer, helping to destroy tumours and save lives. Because these treatments use high‑energy radiation directed at specific parts of the body, accuracy is critical - regardless of how small the dose is. Even small inaccuracies can affect how well a tumour is treated or increase the risk of side effects.
This is where dosimetry plays a vital role. Dosimetry measures how much radiation is delivered during medical procedures and ensures that patients receive exactly the dose prescribed. Reliable dose measurement is essential for safe and effective radiotherapy, diagnostic imaging and nuclear medicine.
The IAEA works with countries to strengthen dosimetry practices through standards, audits, training and laboratory support.
For more than six decades, the IAEA Dosimetry Laboratory in Seibersdorf, Austria - established in 1961 and now modernized through the IAEA's Renovation of the Nuclear Applications Laboratories projects - has been helping countries strengthen the accuracy of their radiation measurements. Through calibration services, audits, training and scientific support, the Laboratory helps ensure that cancer patients worldwide can receive safe and accurate doses.
In October 2025, the IAEA inaugurated the Curie‑Meitner Nuclear Applications Centre in Seibersdorf, completing the modernization project. This new facility is a major upgrade to the IAEA's nuclear science and applications laboratories, strengthening the support provided to countries using nuclear technology for peaceful purposes.
We spoke to Zakithi Msimang, an IAEA medical radiation physicist.
How does the Dosimetry Laboratory's work contribute to improving patient safety and effectiveness in radiotherapy globally?
The IAEA Dosimetry Laboratory provides two services which are critical for patient treatment: calibration and audit services. These services help hospitals deliver the radiation dose prescribed for each patient. Calibration ensures that medical facilities can measure doses accurately. Audits verify that doses are calculated and delivered accurately. Together, these services enable medical physicists to have confidence in their dosimetry system, contributing to patient safety and effective treatment worldwide.
How have the dosimetry services that the IAEA provides to countries evolved over the years?
Over the years the Dosimetry Laboratory has upgraded the equipment it uses for dose audits to increase their precision and lower their cost.
The Dosimetry Laboratory was established to develop a calorimeter and a postal dose audit system for comparing radiation doses between hospitals. Early pilot postal dose inter-hospital comparisons were conducted by the IAEA in 1965-1966 using Fricke dosimeters and Thermo Luminescence Dosimeters (TLDs). Eventually, the service was established based on TLDs due to their good precision, low cost and ease of shipment and it operated this way until 2016. In 2017, the IAEA modernized its systems by replacing ageing TLD readers with radiophotoluminescent dosimetry (RPLD) systems.
Calibration services have also evolved. Initially limited to air-based measurements, they now include absorbed dose to water using cobalt-60 photon beams. The laboratory has also added calibration for high-dose-rate brachytherapy, expressed in terms of reference air kerma rate, and provides X-ray calibrations for both radiation therapy beams and diagnostic radiology.
What approaches have been used to strengthen dosimetry capabilities in low- and middle-income countries?
The IAEA works with the International Centre for Theoretical Physics to offer postgraduate training, including a Master of Advanced Studies in medical physics and, from 2026, a Master of Advanced Studies in radiation metrology. These programmes mainly enroll students from low- and middle-income countries. Together, we have also supported and hosted workshops on a wide range of dosimetry topics.
An IAEA dosimetrist conducting a training session at the Dosimetry Laboratory to strengthen the quality assurance capabilities of cancer centres across the globe. (Photo: G. Velez/IAEA).
How does the IAEA support training and education for medical physicists and dosimetry professionals from around the world?
The IAEA publishes guidance on dosimetry for medical physicists in radiation therapy, nuclear medicine, diagnostic radiology and radiation metrologists. It also issues recommended curricula for medical physicists and radiation metrologists.
Training activities range from regional and national courses to specialized workshops for medical physicists and radiation metrologists on various dosimetry topics hosted and funded by the IAEA, the International Centre for Theoretical Physics, Argonne National Laboratory, IAEA Collaborating Centres and Rays of Hope anchor centres . These have a theoretical and practical hands-on component.
The IAEA also facilitates collaboration among experts through technical meetings for secondary standards dosimetry laboratories and the dosimetry audit network providers. Every seven to eight years, it hosts the International Symposium on Standards, Application and Quality Assurance in Medical Radiation Dosimetry (IDOS).
How do you foster innovation and continuous improvement among the Laboratory's scientific and technical staff?
The recent modernization of the Seibersdorf laboratories - including the new Curie‑Meitner Nuclear Applications Centre - supports innovation in dosimetry by providing upgraded facilities that strengthen scientific collaboration and enhance the development of advanced tools to ensure accurate and safe radiation measurements.
IAEA coordinated research projects (CRPs) foster innovation and continuous improvement. Current CRPs address dosimetry in brachytherapy, diagnostic radiology and a doctoral research project in radiation metrology. Laboratories are encouraged to collaborate with their counterparts in the IAEA/WHO SSDL Network rather than working in isolation.
Inauguration of ReNuAL2 Facilities held at the IAEA Laboratories in Seibersdorf, Austria. 7 October 2025. (Photo: D.Calma/IAEA).
Looking ahead, what major trends do you see shaping the future of global dosimetry and radiation metrology?
Rapid technological development in medical radiation therapy and imaging requires closer coordination between equipment manufacturers and radiation metrologists to ensure that solutions are available more quickly. Today, a significant gap often exists between the introduction of a new technology and the availability of globally accepted calibration and measurement protocols. Closing this gap will require collaboration among developers, regulators, metrology institutes, hospitals and international organizations from the earliest stages of technology development.
