Remote beam output audits: A global assessment of results out of tolerance

Abstract

Background and Purpose: Remote beam output audits, which independently measure an institution’s machine calibration, are a common component of independent radiotherapy peer review. This work reviews the results and trends of these audit results across several organisations and geographical regions. Materials and Methods: Beam output audit results from the Australian Clinical Dosimetry Services, International Atomic Energy Agency, Imaging and Radiation Oncology Core, and Radiation Dosimetry Services were evaluated from 2010 to the present. The rate of audit results outside a +/−5% tolerance was evaluated for photon and electron beams as a function of the year of irradiation and nominal beam energy. Additionally, examples of confirmed calibration errors were examined to provide guidance to clinical physicists and auditing bodies. Results: Of the 210,167 audit results, 1323 (0.63%) were outside of tolerance. There was a clear trend of improved audit performance for more recent dates, and while all photon energies generally showed uniform rates of results out of tolerance, low (6 MeV) and high (≥18 MeV) energy electron beams showed significantly elevated rates. Twenty nine confirmed calibration errors were explored and attributed to a range of issues, such as equipment failures, errors in setup, and errors in performing the clinical reference calibration. Forty-two percent of these confirmed errors were detected during ongoing periodic monitoring, and not at the time of the first audit of the machine. Conclusions: Remote beam output audits have identified, and continue to identify, numerous and often substantial beam calibration errors.

Monte Carlo verification of the holder correction factors for the radiophotoluminescent glass dosimeter used by the IAEA in international dosimetry audits

“…Linac beam qualities (4, 6, 10, 15 and 18 MV) were modeled using the spectra published in the PRIMO project website. 2 The procedure used for obtaining these energy distributions is explained by Brualla et al [20].…”

“…The agreement is deemed acceptable if the IAEA measured and participant stated doses differ by less than 5%. Any results outside this acceptance criterion are followed-up to identify possible causes and resolve discrepancies [2]. This procedure aims at preventing adverse effects on patients originated from dosimetry errors.…”

IAEA methodology for on-site end-to-end IMRT/VMAT audits: an international pilot study

“…IAEA methodology for on-site end-to-end IMRT/VMAT audits: an international pilot study Introduction During the last decades, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) have become widespread around the world. At the same time, external auditing capabilities for radiotherapy (RT) institutions in many countries are limited to the measurement of the absorbed dose to water in reference conditions, which is provided by several dosimetry audit networks (DANs) including the International Atomic Energy Agency (IAEA) in collaboration with the World Health Organization (WHO) [1][2][3]. Meanwhile, implementation of modern RT techniques leads to optimal patient treatment outcomes when supported by comprehensive local quality assurance (QA) programs and external audits [4][5][6][7][8].…”

A comparison of IROC and ACDS on‐site audits of reference and non‐reference dosimetry

“…Independent audits of dosimetry in radiotherapy clinics are an excellent quality improvement tool for detecting systemic errors in dosimetry and encouraging consistency in radiotherapy practice. Dosimetry audits are recognized as international best practice for departmental quality assurance and clinical trial accreditation and have uncovered systemic problems with radiotherapy dose determination, such as dosimetric inaccuracies in heterogeneous dose calculations and small field dose calculations, as well as identifying unique errors in calibration and dose determination at individual clinics …”

“…Dosimetry audits are recognized as international best practice for departmental quality assurance and clinical trial accreditation and have uncovered systemic problems with radiotherapy dose determination, such as dosimetric inaccuracies in heterogeneous dose calculations [1][2][3][4] and small field dose calculations, [5][6][7] as well as identifying unique errors in calibration and dose determination at individual clinics. 8,9 Dosimetry audits can test different elements of the radiotherapy chain, including a simple check of reference dosimetry (Level I audit), increasing in complexity to an end-to-end dose delivery evaluation (Level III). [10][11][12] An intermediate (Level II) audit is one that probes the commissioning data and development of the treatment planning system (TPS) beam model.…”