Objectives: Regional interdepartmental dosimetry audits within the UK provide basic assurances of the dosimetric accuracy of radiotherapy treatments.
Methods: This work reviews several years of audit results from the South East Central audit group including megavoltage (MV) and kilovoltage (kV) photons, electrons and iodine-125 seeds.
Results: Apart from some minor systematic errors that were resolved, the results of all audits have been within protocol tolerances, confirming the long-term stability and agreement of basic radiation dosimetric parameters between centres in the audit region. There is some evidence of improvement in radiation dosimetry with the adoption of newer codes of practice.
Conclusion: The value of current audit methods and the limitations of peer-to-peer auditing is discussed, particularly the influence of the audit schedule on the results obtained, where no "gold standard" exists. Recommendations are made for future audits, including an essential requirement to maintain the monitoring of basic fundamental dosimetry, such as MV photon and electron output, but audits must also be developed to include new treatment technologies such as image-guided radiotherapy and address the most common sources of error in radiotherapy.