IAEA Dosimetry Laboratory Celebrates 50 Years of Work in Medical Dosimetry
This year, the IAEA commemorates the 50th anniversary of its Dosimetry Laboratory in Seibersdorf, Austria, which has played an integral role in improving the consistency of dosimetry used in radiation medicine and other applications of ionizing radiation worldwide. Dosimetry is a precise art of measurement to determine the dose--or the amount of radiation energy-- deposited in a unit mass of matter, such as the cancer cells of a cancer patient. By improving dosimetry measurements around the world, the IAEA helps to ensure that cancer patients treated with radiation beams receive the correct doses, no matter where in the world they are being treated.
A Brief History of the Dosimetry Laboratory
The IAEA Dosimetry Laboratory was set up in 1961 with the aim of preparing a dosimetry system suitable for postal dose comparisons amongst radiotherapy hospitals. At that time, there were no dosimetry standards for the beam calibrations in radiotherapy, making it a challenge for medical physicists working in hospitals to calibrate their radiotherapy beams and guarantee their patients were getting the correct doses. When the IAEA established a postal dose inter-hospital comparison it proved to be a major step in ensuring the accurate calibration of clinical radiation beams. As soon as 1969, the Dosimetry Laboratory sent out the first batch of thermoluminescent dosimeters (TLDs) to radiotherapy hospitals under the ’Joint IAEA/WHO Dose Intercomparison Service for Radiotherapy' project.
In the next decade, further efforts were made to standardize dosimetry measurements in hospitals and other institutions by establishing national standards laboratories in Member States. This lead to the creation of the IAEA/WHO Network of Secondary Standards Dosimetry Laboratories (SSDLs) in 1976. The SSDL Network started with three laboratories—the Dosimetry Lab in Seibersdorf acting as the Central Laboratory—but increased to over 30 in just one year.
The Role of the Dosimetry Laboratory Today
Today, 35 years after its inception, the IAEA/WHO SSDL Network consists of 85 laboratories in 67 countries. The IAEA has provided support for the establishment of many SSDLs in developing countries and by calibrating dosimeters for them, the Dosimetry Laboratory transfers its dosimetry standards to the national level.
It also organizes inter-laboratory comparisons to verify the quality of dosimetry calibrations, and operates dosimetry audit services to make certain that the dose measurements by SSDLs are kept within internationally accepted levels. While the calibration enables users to measure the dose so that it is linked to the international measurement system (SI), the dosimetry audit verifies they have done the job properly.
Each year the Dosimetry Lab calibrates more than 50 ionization chamber systems and independently checks and verifies some 500 beams from radiotherapy equipment in hospitals across the globe. By 2011, the IAEA/WHO TLD audit service had verified the calibration of more than 8000 radiotherapy beams in about 1800 hospitals in over 120 countries. Without this independent audit, discrepancies in the beam calibrations may go unnoticed and patients can receive incorrect treatment. The TLD service has recorded that approximately 95% of the beams audited have adequate calibration. This is quite an improvement from the early years, when it only recorded approximately 50%.
The Dosimetry Laboratory’s job is to raise alarm bells before accidents occur, improve quality controls and help to standardize dosimetry practices globally. It is their mission to ensure cancer patients, wherever they may be, get the safe and effective radiation therapy they need.
The IAEA Dosimetry Laboratory has just finalized the establishment of a new calibration system for X-ray diagnostic radiology. This new service is now available to the SSDL Network Member and will lead to improved accuracy of dosimetry in this field for the benefit of patients undergoing radiation-based imaging modalities.
Nevertheless, while the IAEA is pleased to commemorate the Dosimetry Laboratory for its progress, accomplishments and on-going work in this field, they understand that the work is far from over.