Code of Practice for high-energy photon therapy dosimetry based on the NPL absorbed dose calibration service

Lillicrap, S C; Owen, B.; Williams, J. Raymond; Williams, Peter C.

doi:10.1088/0031-9155/35/10/301

Cited by 144 publications

(82 citation statements)

References 3 publications

(1 reference statement)

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“…As one example, within the UK, repeated reference dosimetry audits have demonstrated that standard deviations (SDs) of the distribution of differences between measured and expected doses and the incidence of out-of-tolerance discrepancies have decreased, indicating improved consistency at the level of beam calibration in the UK. The reasons for this are likely to include the introduction of simple and direct absorbed dose-to-water codes of practice, 38,39 the impact of the audits themselves, the implementation of quality management systems in radiotherapy and regular clinical and dosimetry quality audits via the peerreview standard process and the regional dosimetry audit network, respectively. The options for audit groups are therefore to either tighten tolerances for standard audits or continually develop to include more complexity when it is observed that the original levels are met.…”

Section: Dosimetry Audit Justification and Methodologiesmentioning

confidence: 99%

“…The current UK Code of Practice for MV photon beam dosimetry is the Institute of Physical Sciences in Medicine (IPSM) 1990 code of practice. 38 This was the world's first direct absorbed dose-towater-based protocol. It was developed in collaboration between the NPL, IPSM (now IPEM) and hospital medical physicists and was based on a pioneering national standard using graphite calorimeters.…”

Section: The National Physical Laboratory's Involvement In Auditmentioning

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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Section: Dosimetry Audit Justification and Methodologiesmentioning

confidence: 99%

Section: The National Physical Laboratory's Involvement In Auditmentioning

confidence: 99%

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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“…These calibrations are used with the UK Codes of Practice [5, 6] as the basis for reference dosimetry in UK clinics.…”

Section: Review Of Calibration Services Outside Australiamentioning

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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“…Determination of the beam spectrum in a clinical environment is not practical and for this reason dosimetry codes of practice recommend the use of a beam quality specifier or beam quality index ͑Q͒, which can be easily derived either from depth dose or tissue phantom ratio measurements. [1][2][3][4] The beam quality index, as defined by the TPR 20,10 ͑10ϫ 10 cm 2 ͒, is the ratio of water absorbed doses on the beam axis at the depths of 20 and 10 cm in a water phantom obtained at a constant source-detector distance of 100 cm and a 10ϫ 10 cm 2 field size at the position of the detector. 3 Note that the TG 51 protocol uses the percentage depth dose at 10 cm as the beam quality parameter.…”

Section: Introductionmentioning

confidence: 99%