Accuracy required and achievable in radiotherapy dosimetry: have modern technology and techniques changed our views?

Thwaites, David

doi:10.1088/1742-6596/444/1/012006

Cited by 82 publications

(72 citation statements)

References 41 publications

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“…22 The average 3D gamma for PTV's and OAR's for twenty patients used in this study were less than the recommended value of 0.6 by Visser et al 17 In three pelvis cases due to low dose of bowel, the percentage difference of average dose was more than 10%. DVH in COMPASS provides many statistical tools; however, we cannot judge plan quality by choosing one criteria, as the percentage difference in average dose, dose at volume and volume at dose will be too high for structure lying in low dose region.…”

Section: Discussioncontrasting

confidence: 50%

Pretreatment quality assurance of volumetric modulated arc therapy on patient CT scan using indirect 3D dosimetry system

Swamy

Chandrasekaran

Kathirvel

et al. 2014

Int J Cancer Ther Oncol

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Purpose: Aim of this study is to clinically implement the COMPASS 3D dosimetry system for pretreatment quality assurance of volumetric modulated arc therapy (VMAT-RapidArc) treatment plans. Methods: For this study, 10 head and neck (H&N) and pelvis VMAT plans dose response from Linac was measured using COMPASS system along with MatriXX Evolution and 3D dose reconstructed in the patient computed tomography (CT) scan. Dose volume histograms and 3D gamma were used to evaluate difference between the measured and calculated values. In order to validate the COMPASS system, dose response for open fields were acquired for both homogeneous and inhomogeneous phantoms. Results: The average dose difference between Eclipse treatment planning system (TPS) calculated and COMPASS measured (homogenous medium) in normalization region, inner region, penumbra region and buildup region was less than ±2%. In inhomogeneous phantom, there was a maximum difference -3.17% in lung, whereas the difference other densities was within ±2%. The systematic increase in the average 3D gamma between the TPS calculated and COMPASS measured for VMAT plans with known dose errors and multi-leaf collimator (MLC) offset errors shows that COMPASS system was sensitive enough to find clinical significant errors. The 3D dose parameters (D95, D1, and average dose) of all H&N and pelvis patients were well within the clinically acceptable tolerance level of ±5%. The average 3D gammas for planning target volumes (PTV) and organ at risks (OAR) of the patients were less than 0.6. Conclusion:The results from this study show that COMPASS along with MatriXX Evolution can be effectively used for pretreatment verification of VMAT plans in the patient anatomy.

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Section: Discussioncontrasting

confidence: 50%

Pretreatment quality assurance of volumetric modulated arc therapy on patient CT scan using indirect 3D dosimetry system

Swamy

Chandrasekaran

Kathirvel

et al. 2014

Int J Cancer Ther Oncol

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“…[1][2][3][4][5] Recommendations by the International Commission of Radiation Units and Measurements in 1976 1 state that the dose delivery to the primary target should be within 65% of the prescribed value (but in some special circumstances 62%). These are based on assessments of clinical accuracy requirements and set the tolerances for process and equipment performance and quality assurance, as well as audit tolerances.…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, awareness of patient positioning and other geometric uncertainties has been mandated, in terms of target coverage and organs-at-risk (OARs) avoidance, but also because geometric uncertainties translate directly into dosimetric uncertainties, increasingly so as techniques become more complex. 5 The value of 5% consists of contributions mainly from dose-calculation accuracy, patient positioning including target and organ definition and treatment machine mechanical tolerance.…”

Section: Introductionmentioning

confidence: 99%

“…Together, their results can identity demonstrable benefits and effectiveness and can contribute to estimates of the currently achieved consistency in radiotherapy dosimetry. 5 They can demonstrate the role of dosimetry audits in helping assure accuracy of advanced radiotherapy techniques, determine their benefits to clinical trials and inform the arguments for further national/international audits. As radiotherapy planning and treatment delivery have become less intuitive and more automated, a willingness to undergo radiation dosimetry audit, as one vital component in wider clinical audit, demonstrates the best practice and transparency in the overall process and is now an intrinsic part of the radiation oncology requirements in the national cancer peer-review standards 33 and of acceptability to enter patients into clinical trials involving radiotherapy.…”

Section: Introductionmentioning

confidence: 99%

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Radiotherapy dosimetry audit: three decades of improving standards and accuracy in UK clinical practice and trials

Clark

Aird

Bolton

et al. 2015

BJR

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Dosimetry audit plays an important role in the development and safety of radiotherapy. National and large scale audits are able to set, maintain and improve standards, as well as having the potential to identify issues which may cause harm to patients. They can support implementation of complex techniques and can facilitate awareness and understanding of any issues which may exist by benchmarking centres with similar equipment. This review examines the development of dosimetry audit in the UK over the past 30 years, including the involvement of the UK in international audits. A summary of audit results is given, with an overview of methodologies employed and lessons learnt. Recent and forthcoming more complex audits are considered, with a focus on future needs including the arrival of proton therapy in the UK and other advanced techniques such as four-dimensional radiotherapy delivery and verification, stereotactic radiotherapy and MR linear accelerators. The work of the main quality assurance and auditing bodies is discussed, including how they are working together to streamline audit and to ensure that all radiotherapy centres are involved. Undertaking regular external audit motivates centres to modernize and develop techniques and provides assurance, not only that radiotherapy is planned and delivered accurately but also that the patient dose delivered is as prescribed.

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“…Boyer and Schultheiss [21] conclude that 1 % in dose correlates with about a 2 % change in early-stage tumour control. A more recent analysis by Thwaites et al [22] concludes that 3 % standard uncertainty in the dose delivered to the patient can be taken as the “currently recommended general accuracy requirement”. Further discussion can be found in references [20–23].…”

Section: Discussionmentioning

confidence: 99%

Direct megavoltage photon calibration service in Australia

Butler¹,

Ramanathan²,

Oliver³

et al. 2014

Australas Phys Eng Sci Med

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The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) maintains the Australian primary standard of absorbed dose. Until recently, the standard was used to calibrate ionisation chambers only in 60Co gamma rays. These chambers are then used by radiotherapy clinics to determine linac output, using a correction factor (kQ) to take into account the different spectra of 60Co and the linac. Over the period 2010–2013, ARPANSA adapted the primary standard to work in megavoltage linac beams, and has developed a calibration service at three photon beams (6, 10 and 18 MV) from an Elekta Synergy linac. We describe the details of the new calibration service, the method validation and the use of the new calibration factors with the International Atomic Energy Agency’s TRS-398 dosimetry Code of Practice. The expected changes in absorbed dose measurements in the clinic when shifting from 60Co to the direct calibration are determined. For a Farmer chamber (model 2571), the measured chamber calibration coefficient is expected to be reduced by 0.4, 1.0 and 1.1 % respectively for these three beams when compared to the factor derived from 60Co. These results are in overall agreement with international absorbed dose standards and calculations by Muir and Rogers in 2010 of kQ factors using Monte Carlo techniques. The reasons for and against moving to the new service are discussed in the light of the requirements of clinical dosimetry.

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Accuracy required and achievable in radiotherapy dosimetry: have modern technology and techniques changed our views?

Cited by 82 publications

References 41 publications

Pretreatment quality assurance of volumetric modulated arc therapy on patient CT scan using indirect 3D dosimetry system

Pretreatment quality assurance of volumetric modulated arc therapy on patient CT scan using indirect 3D dosimetry system

Radiotherapy dosimetry audit: three decades of improving standards and accuracy in UK clinical practice and trials

Direct megavoltage photon calibration service in Australia

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