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Dosimetry audit


The optimum clinical outcome for a patient receiving a course of external beam radiotherapy is critically dependent upon the accurate calibration of the treatment unit. Although 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 closely monitored for stability over the lifetime of the device, it is prudent to obtain independent confirmation of calibration accuracy.

Important Principles

Various laboratories across the globe offer remote monitoring of therapeutic radiation beams through mailed out thermoluminescence dosimeters or other devices which can store information about the radiation dose they have received. Although typically not as accurate as an on-site dose determination with an accurately calibrated ionization chamber, postal audits are convenient, relatively cheap and can serve to identify treatment machine calibration errors in different irradiation geometries. Particularly when a new technology is being introduced, such as Intensity Modulated Radiation Therapy, mailed out dosimeters can verify that the data in the treatment planning system accurately describes the treatment beam.

Introduction to References

The book chapter briefly describes the key features of the IAEA’s auditing programmes. Details of the postal dosimetry service and on-site physics audit are also given. The IAEA dosimetry Laboratory is the centre of the IAEA/WHO Network of Secondary Standards Dosimetry Laboratories which is described in the IAEA TECDOC. More information about the IAEA program can be found here.

Role of Quality Audits: View from the IAEA. J. Izewska and Eeva Salminen. In Quality and Safety in Radiotherapy. Eds T. Pawlicki et al. CRC press

A methodology for TLD postal dosimetry audit of high-energy radiotherapy photon beams in non-reference conditions. J. Izewska et al. Radioth Oncol 84 (2007) 67-74

IAEA-TECDOC-1543 On-site Visits to Radiotherapy Centres: Medical Physics Procedures. IAEA, Vienna

SSDL Newsletter No. 58. IAEA, Vienna

Data forms and instructions for participation in IAEA/WHO TLD Postal Dose Audit service as well as a TLD irradiation video are available in English, Spanish and Russian and can be downloaded.