NCS Report 10: Dosimetry of low and medium energy X-rays

Grimbergen, T.W.M.; Aalbers, A.H.L.; Mijnheer, B.J.; Thierens, Hubert; Dam, J. Van; Wittkämper, F.W.; Zoetelief, J.

doi:10.25030/ncs-010

Cited by 15 publications

(10 citation statements)

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“…We have found an agreement between D w measured by the calorimeter and determined through an air-kerma based dosimetry protocol to better than 1%, which is considerably smaller than both the uncertainties estimated at ENEA-INMRI for the determination of D w by the in-water-phantom graphite calorimeter or for the air-kerma-based D wK determination. Although our comparison of D w measurements is limited to one type of Farmer chamber and one dosimetric protocol, it is worth noting that other investigators have reported similar results with agreements within 2% at the same radiation qualities studied in this work (de Prez and de Pooter 2008) using the NCS-10 dosimetry protocol (Grimbergen et al 1997), or within 1.5%, using the same filtered x-ray radiation qualities, but several types of chambers, and in comparison with several dosimetry protocols (Perichon et al 2013). In all of these cases, the agreement between D w and D wK was better than the stated uncertainties.…”

Section: Discussionsupporting

confidence: 62%

“…In fact, for this chamber model, Krauss et al (2012) were able to determine p Q with an uncertainty of 0.6% by calibrating their chamber against their D w and K a primary standards. However, for other types of chambers, the uncertainty on p Q can be considerably larger, due to the differences observed among chambers and radiation qualities, leading to an uncertainty on D wK that is typically about 3% (Grimbergen et al 1997, Andreo et al 2000, Ma et al 2001, Aukett et al 2005.…”

Section: Discussionmentioning

confidence: 99%

“…A type B uncertainty in the ratio of water-to-air mass attenuation coefficients is set to 1.5%, according to international dosimetry protocols (Ma et al 2001, Aukett et al 2005. The factors p Q are typically reported in the dosimetry protocols with an uncertainty of 1.5%-3% to take into account the variability in their experimental determinations (Andreo et al 1997, Grimbergen et al 1997, Ma et al 2001, Aukett et al 2005. In this work, we have adopted p Q values from (Krauss et al 2012) who reported a type B uncertainty of 0.6% for their measurements.…”

Section: Ccrimentioning

confidence: 99%

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A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams

et al. 2016

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The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.

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Section: Discussionsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Section: Ccrimentioning

confidence: 99%

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A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams

et al. 2016

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“…The measurement of percentage depth dose (PDD) curves for kilovoltage x-ray beams, especially near the surface, is subject to problems related to large gradients in the dose distribution and the large energy dependence of most dosimetry systems (Grimbergen et al 1998).…”

Section: Introductionmentioning

confidence: 99%

An assessment of GafChromic film for measuring 50 kV and 100 kV percentage depth dose curves

Fletcher

Mills

2008

Phys. Med. Biol.

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Percentage depth dose (PDD) curves were obtained for 50 kV and 100 kV x-rays on a Gulmay Medical D3000 DXR unit. Different dosimetry systems were compared including a Scanditronix Wellhofer small volume cylindrical ion chamber, a Wellhofer photon PFD diode, a PTW soft x-ray parallel plate chamber (N23342) and two types of radiochromic film: GafChromic EBT and GafChromic MD55. The PDD curves were also compared to BEAMnrc Monte Carlo predictions. GafChromic film was found to be a valid choice of dosimeter for measuring percentage depth dose curves at 100 kV and 50 kV. All the dosimeters showed agreement with predictions at depths greater than 10 mm, while near the surface GafChromic film and PFD diodes give the best agreement to Monte Carlo values.

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“…This measurement is defined by international standard protocols, considering different energy ranges. The recommended dosimetry protocols for low and medium x rays are: TRS#277 1 and TRS#398 2 from the International Atomic Energy Agency (IAEA); TG#61 3 from the American Association of Physicists in Medicine (AAPM); and NCS#10 4 from the Institution of Physics and Engineering in Medicine and Biology (IPEMB) 5 . The IAEA TRS#277, AAPM TG#61, and IPMB NCS#10 are the protocols specifically for medium‐energy x rays, and are the standard protocols used at the Brazilian National Ionizing Radiation Metrology Laboratory (LNMRI).…”

Section: Introductionmentioning

confidence: 99%

Determination of the absorbed dose to water for medium‐energy x‐ray beams using Fricke dosimetry

et al. 2020

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Purpose For x‐ray beams in the low and medium energy range, reference dosimetry is established in terms of air kerma. Fricke dosimetry has shown great potential in the absolute measurements of the absorbed dose to water for high‐energy ranges. Therefore, the main purpose of this work was to compare the absorbed dose to water for medium‐energy x‐ray beams obtained through Fricke dosimetry with that obtained from the air kerma rate. Methods To determine the absorbed dose to water using Fricke dosimetry, the polyethylene bags methodology was chosen. Fricke solution was irradiated at four different beam qualities. The absorbed dose to water values obtained using Fricke dosimetry were compared to those obtained using the standard protocol, using the Z‐score. Results Values of the Z‐score were <2 for all measurements of absorbed dose to water, which means that the values obtained using Fricke dosimetry are equivalent to those obtained using the reference protocol. The combined standard uncertainty for the absorbed dose to water obtained by Fricke dosimetry was lower than that obtained with the ionization chamber. Conclusions Chemical dosimetry using a standard FeSO4 solution has been demonstrated to be a potential option as a standard for the quantity absorbed dose to water for medium kV x‐ray qualities.

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NCS Report 10: Dosimetry of low and medium energy X-rays

Cited by 15 publications

References 0 publications

A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams

A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams

An assessment of GafChromic film for measuring 50 kV and 100 kV percentage depth dose curves

Determination of the absorbed dose to water for medium‐energy x‐ray beams using Fricke dosimetry

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