The IAEA has developed a brachytherapy dosimetry methodology which serves as the basis for a new audit service provided by the Agency's Dosimetry Laboratory. For millions of cancer patients around the world, particularly those in resource-constrained contexts, the results of this multicentre pilot study led by the IAEA will help ensure the safety and effectiveness of their high-dose rate brachytherapy treatments.
The new methodology was developed under an ongoing coordinated research project that brought together nearly 50 centres from 11 different countries.
High-dose rate (HDR) brachytherapy is a type of radiation therapy used to treat cervical, prostate and other cancers. It delivers radiation directly to a patient's tumour through a miniaturized radioactive source placed inside the patient's body. While this approach minimizes the exposure of surrounding healthy tissues to radiation, HDR brachytherapy also presents a unique treatment challenge: it delivers significantly higher doses than external beam radiotherapy. Consequently, HDR requires meticulous optimization to avoid adverse effects from under- or over-dosage. Dosimetry audits - which can help check the accuracy of radiation doses - are not only crucial to quality and safety but can also improve public confidence in this treatment option.
Despite their importance, dosimetry audits in brachytherapy are not as widely available as those in external beam radiotherapy. In response, the IAEA launched a coordinated research project (CRP E24023) in 2021 to develop a dedicated dosimetry audit methodology for HDR brachytherapy.
Developing the Audit Method
An initial meeting of the project's research teams from 10 different countries (Brazil, China, Croatia, Greece, India, Iran, Mexico, the Russian Federation, South Africa and Spain) explored various potential audit designs. Central to such a methodology are phantoms, which are specially designed devices that medical physicists use to assess radiation doses with the requisite accuracy.
With simulations providing a theoretical basis, the IAEA's Dosimetry Laboratory was able to create a small, lightweight and easy-to-transport phantom. The device measures 16 centimetres by 8 centimetres by 3 centimetres and contains a radiophotoluminescent dosimeter to measure delivered doses and radiochromic films to check the accuracy of the source's position. The phantom can be constructed from widely available materials and can be used with interstitial plastic catheters. This means the phantom does not require a specific manufacturer, making it cost-effective, accessible and practical for hospitals and facilities around the world.
The methodology utilizes a reference treatment plan that can be used on all major commercially available treatment planning systems and HDR afterloader systems and was tested in 54 centres internationally. With some facilities performing more than one irradiation, the IAEA received a total of 59 measurements - 45 of which were irradiated with iridium-192 and 14 with a cobalt-60 source across 49 different brachytherapy afterloaders of various models.
"The results of this multicentre pilot study validate the dosimetry audit methodology, demonstrating its accuracy, reliability and accessibility for global use," noted Alexis Dimitriadis, the laboratory's previous Quality Manager in the IAEA Division of Human Health. The method's development and testing as well as its Monte Carlo simulated correction factors have been published in the journal Physics and Imaging in Radiation Oncology.
"A testament to the vital role the IAEA's human health programme plays in supporting countries around the world, the study builds on existing scientific endeavours within the field of dosimetry audits for radiotherapy," said Jamema Swamidas, Head of DOL in the IAEA Division of Human Health. "Its results contribute to the coordinated research project's overarching aim and ongoing work on a multi-level audit methodology that includes an end-to-end audit of the entire brachytherapy workflow from imaging to treatment planning to delivery."
The IAEA encourages hospitals to apply to participate in the newly launched dosimetry audit when they commission their HDR brachytherapy afterloaders.
The easy-to-transport IAEA brachytherapy auditing kit which contains a phantom, RPLDs and radiochromic films. (Photo: K. Chelminski/IAEA)
