IAEA quality audits in radiotherapy

Iżewska, J.; Bera, P.; Azangwe, G.; Grochowska, P.; Meghzifene, Ahmed

doi:10.1016/j.ejmp.2014.07.054

Cited by 3 publications

(3 citation statements)

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“…The reason for choosing 6 MV as a working incident spectrum is based on the predominant use of this energy worldwide, according to the most recent compilations of the International Atomic Energy Agency (IAEA) and the Imaging and Radiation Oncology Core (IROC) Houston QA Center (formerly the Radiological Physics Center, RPC). Their databases show that worldwide approximately 75% of the more than 9000 clinical accelerators registered have nominal accelerator potentials of 10 MV or less (Izewska 2014), a percentage that decreases to about 70% in the USA (Followill 2014). As will be discussed below, 50% of the absorbed dose at a depth of 10 cm in water by 6 MV and 15 MV photon beams is due to electrons with energies approximately below 0.6 MeV and 1.3 MeV, respectively.…”

Section: Calculation Of Electron Spectramentioning

confidence: 99%

Dose to ‘water-like’ media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate

Andreo

2014

Phys. Med. Biol.

105

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The difference between Monte Carlo Treatment Planning (MCTP) based on the assumption of 'water-like' tissues with densities obtained from CT procedures, or on tissue compositions derived from CT-determined densities, have been investigated. Stopping powers and electron fluences have been calculated for a range of media and body tissues for 6 MV photon beams, including changes in their physical data (density and stopping powers). These quantities have been used to determine absorbed doses using cavity theory. It is emphasized that tissue compositions given in ICRU or ICRP reports should not be given the standing of physical constants as they correspond to average values obtained for a limited number of human-body samples. It has been shown that mass stopping-power ratios to water are more dependent on patient-to-patient composition differences, and therefore on their mean excitation energies (I-values), than on mass density. Electron fluence in different media are also more dependent on media composition (and their I-values) than on density. However, as a consequence of the balance between fluence and stopping powers, doses calculated from their product are more constant than what the independent stopping powers and fluence variations suggest. Additionally, cancelations in dose ratios minimize the differences between the 'water-like' and 'tissue' approaches, yielding practically identical results except for bone, and to a lesser extent for adipose tissue. A priori, changing from one approach to another does not seem to be justified considering the large number of approximations and uncertainties involved throughout the treatment planning tissue segmentation and dose calculation procedures. The key issue continues to be the composition of tissues and their I-values, and as these cannot be obtained for individual patients, whatever approach is selected does not lead to significant differences from a water reference dose, the maximum of these being of the order of 5% for bone tissues. Considering, however, current developments in advanced dose calculation methods, planning in terms of dose-to-tissue should be the preferred choice, under the expectancy that progress in the field will gradually improve some of the crude approximations included in MCTP and numerical transport methods. The small differences obtained also show that a retrospective conversion from dose-to-tissue to dose-to-water, based on a widely used approach, would mostly increase the final uncertainty of the treatment planning process. It is demonstrated that, due to the difference between electron fluence distributions in water and in body tissues, the conversion requires an additional fluence correction that has so far been neglected. An improved expression for the conversion and data for the fluence correction factor are provided. These will be necessary even in a dose-to-tissue environment, for the normalization of the treatment plan to the reference dosimetry of the treatment unit, always calibrated in terms of absorbed dose to water.

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Section: Calculation Of Electron Spectramentioning

confidence: 99%

Dose to ‘water-like’ media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate

Andreo

2014

Phys. Med. Biol.

105

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“…QUATRO assesses overall practices in radiotherapy centres including the infrastructure, patient and equipment procedures, quality assurance programmes, radiation protection, staffing levels and professional training of the local radiotherapy staff. It has conducted over 70 audits on request, in radiotherapy centres of Central and Eastern Europe, Asia, Africa, and Latin America contributing to the improvement at the audited centres [14].…”

Section: Introductionmentioning

confidence: 99%

Medical Physics: Forming and testing solutions to clinical problems

Tsapaki

Bayford

2015

Physica Medica

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“…Currently, in Malaysia there are 25 radiotherapy centres comprising 7 government hospitals and 18 private medical centres, serving a population of 31.7 million people in 2016. As a member of a state of the International Atomic Energy Agency (IAEA), Malaysia has participated in a project called "IAEA/WHO Thermoluminesence Dosimeter (TLD) Postal Audit Program" [1]. The objective was to provide a quality audit on the dose delivered by megavoltage X-ray teletherapy units for radiotherapy centres worldwide.…”

Section: Introductionmentioning

confidence: 99%

The influence of annealing temperature and heating rate on thermoluminescence properties of nanocrystalline calcium borate powder

2017

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Abstract. We have reported the influence of annealing temperature and heating rate on thermoluminescence (TL) properties of nanocrystalline calcium borate, CaB2O4, powder synthesized by solution combustion method. Powder X-ray diffraction experiments were carried out on CaB2O4 to get the crystal phase and size. The samples were annealed using the TLD oven and exposed to cobalt-60 source. TL glow curves were measured and recorded using a Harshaw model 3500 TLD reader. The crystal phase confirmed one major phase of CaB2O4 with 27 nm in size. CaB2O4 has a simple glow curve with only one and a well defined peak at around 150 °C. TL intensity was higher after annealing the material before irradiation which indicated the importance of annealing. It was found that an annealing temperature at 300 °C for one hour and the heating rate of 10 °C s -¹ was the best procedure to produce high TL intensity.

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IAEA quality audits in radiotherapy

Cited by 3 publications

References 0 publications

Dose to ‘water-like’ media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate

Dose to ‘water-like’ media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate

Medical Physics: Forming and testing solutions to clinical problems

The influence of annealing temperature and heating rate on thermoluminescence properties of nanocrystalline calcium borate powder

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