A multinational audit of small field output factors calculated by treatment planning systems used in radiotherapy

Lechner, Wolfgang; Wesolowska, Paulina; Azangwe, G.; Arib, Mehenna; Alves, Victor Gabriel Leandro; Suming, Luo; Ekendahl, Daniela; Bulski, W.; Samper, José Luis Alonso; Vinatha, S.P.; Srimanoroth, Siri; Tomsej, M.; Tenhunen, Mikko; Povall, J.M.; Kry, Stephen F; Followill, David S; Thwaites, David; Georg, Dietmar; Iżewska, J.

doi:10.1016/j.phro.2018.02.005

Cited by 50 publications

(49 citation statements)

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“…This has been recently addressed by the publication of the IAEA code of practice [41] but the accurate modelling of small fields and how the correct detector is used to collect the commissioning data is still challenging. Several groups [11,12,21] conducted national and multi-national audits respectively, of calculated small field output factors by comparing with standardised data published by the IROC-Houston QA center at MD Anderson [22,23,42] and found that not all centres were modelling these fields well. The audits found that the deviations increased with decreasing field size and the treatment planning system commonly overestimated in comparison with the reference data.…”

Section: Advanced Techniquesmentioning

confidence: 99%

“…At an institutional level, an external dosimetry audit provides an independent check of the local approaches and thus supports the implementation of novel and complex techniques [6] , [7] , [13] , [15] , [17] , [18] , [19] , [20] . Where multiple centres have been included in the audit, the process of comparison with other centres facilitates awareness and understanding of issues which may exist and which may not be identified by a single centre alone [5] , [6] , [21] . Furthermore this sharing of experience allows benchmarking of centres with similar equipment and thus increases the knowledge of what is achievable with a particular combination of equipment [22] , [23] .…”

Section: Introductionmentioning

confidence: 99%

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The role of dosimetry audit in achieving high quality radiotherapy

Clark

Jornet

Muren

2018

Physics and Imaging in Radiation Oncology

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Section: Advanced Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The role of dosimetry audit in achieving high quality radiotherapy

Clark

Jornet

Muren

2018

Physics and Imaging in Radiation Oncology

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“…The purpose of this work is to present both the methodology of a new remote end-to-end audit for IMRT/VMAT head treatment delivery and the results obtained in a comprehensive testing phase. This audit aims to provide an independent verification of the radiotherapy chain including imaging, dose calculation, set-up and dose delivery, representing a continuation of previously developed audit methodologies [3,4,24,25]. This remote end-to-end audit methodology was developed under an IAEA CRP and included a multicentre pilot study and national trial runs conducted by various DANs in close cooperation with the IAEA.…”

Section: Introductionmentioning

confidence: 99%

Testing the methodology for a dosimetric end-to-end audit of IMRT/VMAT: results of IAEA multicentre and national studies

et al. 2019

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Introduction: Within an International Atomic Energy Agency (IAEA) coordinated research project (CRP), a remote end-to-end dosimetric quality audit for intensity modulated radiation therapy (IMRT)/ volumetric arc therapy (VMAT) was developed to verify the radiotherapy chain including imaging, treatment planning and dose delivery. The methodology as well as the results obtained in a multicentre pilot study and national trial runs conducted in close cooperation with dosimetry audit networks (DANs) of IAEA Member States are presented. Material and methods: A solid polystyrene phantom containing a dosimetry insert with an irregular solid water planning target volume (PTV) and organ at risk (OAR) was designed for this audit. The insert can be preloaded with radiochromic film and four thermoluminescent dosimeters (TLDs). For the audit, radiotherapy centres were asked to scan the phantom, contour the structures, create an IMRT/VMAT treatment plan and irradiate the phantom. The dose prescription was to deliver 4 Gy to the PTV in two fractions and to limit the OAR dose to a maximum of 2.8 Gy. The TLD measured doses and film measured dose distributions were compared with the TPS calculations. Results: Sixteen hospitals from 13 countries and 64 hospitals from 6 countries participated in the multicenter pilot study and in the national runs, respectively. The TLD results for the PTV were all within ±5% acceptance limit for the multicentre pilot study, whereas for national runs, 17 participants failed to meet this criterion. All measured doses in the OAR were below the treatment planning constraint. The film analysis identified seven plans in national runs below the 90% passing rate gamma criteria. Conclusion: The results proved that the methodology of the IMRT/VMAT dosimetric end-to-end audit was feasible for its intended purpose, i.e., the phantom design and materials were suitable; the phantom was easy to use and it was robust enough for shipment. Most importantly the audit methodology was capable of identifying suboptimal IMRT/VMAT delivery.

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“…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 [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).…”

Section: Introductionmentioning

confidence: 99%

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

Lye¹,

Kry

Shaw³

et al. 2019

Medical Physics

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PurposeConsistency between different international quality assurance groups is important in the progress toward similar standards and expectations in radiotherapy dosimetry around the world, and in the context of consistent clinical trial data from international trial participants. This study compares the dosimetry audit methodology and results of two international quality assurance groups performing a side‐by‐side comparison at the same radiotherapy department, and interrogates the ability of the audits to detect deliberately introduced errors.MethodsA comparison of the core dosimetry components of reference and non‐reference audits was conducted by the Imaging and Radiation Oncology Core (IROC, Houston, USA) and the Australian Clinical Dosimetry Service (ACDS, Melbourne, Australia). A set of measurements were conducted over 2 days at an Australian radiation therapy facility in Melbourne. Each group evaluated the reference dosimetry, output factors, small field output factors, percentage depth dose (PDD), wedge, and off‐axis factors according to their standard protocols. IROC additionally investigated the Electron PDD and the ACDS investigated the effect of heterogeneities. In order to evaluate and compare the performance of these audits under suboptimal conditions, artificial errors in percentage depth dose (PDD), EDW, and small field output factors were introduced into the 6 MV beam model to simulate potential commissioning/modeling errors and both audits were tested for their sensitivity in detecting these errors.ResultsWith the plans from the clinical beam model, almost all results were within tolerance and at an optimal pass level. Good consistency was found between the two audits as almost all findings were consistent between them. Only two results were different between the results of IROC and the ACDS. The measurements of reference FFF photons showed a discrepancy of 0.7% between ACDS and IROC due to the inclusion of a 0.5% nonuniformity correction by the ACDS. The second difference between IROC and the ACDS was seen with the lung phantom. The asymmetric field behind lung measured by the ACDS was slightly (0.3%) above the ACDS's pass (optimal) level of 3.3%. IROC did not detect this issue because their measurements were all assessed in a homogeneous phantom. When errors were deliberately introduced neither audit was sensitive enough to pick up a 2% change to the small field output factors. The introduced PDD change was flagged by both audits. Similarly, the introduced error of using 25° wedge instead of 30° wedge was detectible in both audits as out of tolerance.ConclusionsDespite different equipment, approach, and scope of measurements in on‐site audits, there were clear similarities between the results from the two groups. This finding is encouraging in the context of a global harmonized approach to radiotherapy quality assurance and dosimetry audit.

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A multinational audit of small field output factors calculated by treatment planning systems used in radiotherapy

Cited by 50 publications

References 30 publications

The role of dosimetry audit in achieving high quality radiotherapy

The role of dosimetry audit in achieving high quality radiotherapy

Testing the methodology for a dosimetric end-to-end audit of IMRT/VMAT: results of IAEA multicentre and national studies

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

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