Dosimetry auditing

Radiotherapy machines used for cancer treatment need to be calibrated regularly to ensure that the patient doses are accurate. The IAEA, together with the World Health Organization, offers dose audit services to cancer clinics to help them improve dosimetry practices.

Safe and effective radiotherapy relies to a large extent on accurate dosimetry. Differences as small as 5 per cent from the prescribed radiation dose can change the outcome of treatment. Dosimetry mistakes can also result in radiation injuries, which in serious cases can even lead to death. For this reason, a radiotherapy clinic’s radiation beam should be regularly audited. Such audits are also of benefit to national dosimetry laboratories.

The IAEA maintains the Dosimetry Laboratory in Seibersdorf, Austria, that provides such dose auditing services. It regularly sends out small dosimeters to radiotherapy clinics, which give them a radiation dose as they would for a patient. The devices are then sent back to the IAEA’s Laboratory, where the radiation dose the clinics intended to give is compared with the one they actually gave.

When an audit detects discrepancies, the IAEA Dosimetry Laboratory alerts the clinic in question and asks for a new dosimeter to be irradiated. This follow-up procedure may also include on-site visits by local or international experts. Audit results recorded over the last decades show a steady increase in clinics’ abilities to get the dose right. Today, more than 95 per cent of all results are acceptable.

Similar auditing services are offered to Secondary Standard Dosimetry Laboratories to verify the accuracy of their dosimetry measurements in radiotherapy and radiation protection.

Supporting national audit networks for radiotherapy

The IAEA has supported the establishment of several national audit groups for radiotherapy dosimetry in Member States. It also helped develop the methodology for a range of dosimetry audit levels, from basic to advanced.

Through the link with the IAEA’s Laboratory, the national audit networks closely cooperate at the consecutive stages of developing the dosimetry audit methodology locally and by carrying out cross-measurements. The IAEA Dosimetry Laboratory contributes to strengthening quality assurance of national audit networks by exchanging dosimeters with their dosimetry laboratories. This interlinking of national audit systems helps ensure that international and national radiotherapy dosimetry audit networks are working to consistent levels.