New standards of absorbed dose to water under reference conditions by graphite calorimetry for<sup>60</sup>Co and high-energy x-rays at LNE-LNHB

Delaunay, F.; Gouriou, J.; Daures, J.; Roy, M. Le; Ostrowsky, A.; Rapp, B.; Sorel, S.

doi:10.1088/0026-1394/51/5/552

Cited by 10 publications

(7 citation statements)

References 50 publications

(84 reference statements)

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“…It should be mentioned, for clarification, that the ratios k Q 3x3 /k Q 10x10 would be even larger if the correction factors k v from table 3 had not been applied. To some extent, the finding of an increasing ratio k Q 3x3 /k Q 10x10 is in contrast to other published data (Krauss et al 2011, Delaunay et al 2011, Delaunay et al 2012 which showed no significant variation of the k Q factors with beam size. However, these measurements have not been performed for photon beams with generating voltage higher than 12 MV and from figure 7 it is evident that the conclusion of a linear increase is mainly affected just by the k Q 3x3 /k Q 10x10 value at 25 MV.…”

Section: K Q Factors and Ratios Kcontrasting

confidence: 99%

“…the ratio of k Q factors in the 3 cm × 3 cm and in the reference field (10 cm × 10 cm), was close to one within the standard uncertainty of about 0.4%. A similar result was achieved at Laboratoire National Henri Bequerel (LNE-LNHB), where k Q factors by means of graphite calorimetry were determined in 4 cm × 4 cm and 2 cm × 2 cm beams of 6 MV and 12 MV photons (Delaunay et al 2011). They concluded that the measured k Q values for NE 2577 and Exradin A1SL chambers showed no variation with the beam size within the experimental standard uncertainies.…”

Section: Introductionsupporting

confidence: 72%

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Experimental determination ofk_Qfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Krauss

Kapsch

2014

Phys. Med. Biol.

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For the ionometric determination of absorbed dose to water, Dw, in megavoltage photon beams from a linear accelerator, beam-quality-dependent correction factors, kQ, are used for the ionization chambers. By using a water calorimeter, these factors can be determined experimentally and with substantially lower standard uncertainties compared to calculated values of the kQ, which are published in various dosimetry protocols. In this investigation, kQ for different types of cylindrical ionization chambers (NE 2561, NE 2571, FC 65 G) were determined experimentally in 10 cm × 10 cm photon beams from 4 MV to 25 MV (corresponding beam quality index TPR20,10 from 0.64 to 0.80). The measurements were carried out at the linear accelerator facility of the Physikalisch-Technische Bundesanstalt. It is shown that the kQ factors for a single ionization chamber in 10 cm × 10 cm photon beams can be measured with a relative standard uncertainty of 0.31%. In addition to these measurements in 10 cm × 10 cm fields, kQ factors for the NE 2561 chamber were also determined in smaller 3 cm × 3 cm photon beams between 6 MV and 25 MV. In this case, relative standard uncertainties between 0.35 % and 0.38 % are achieved for the kQ factors. It is found for this ionization chamber, that the ratio of the kQ factors in 3 cm × 3 cm and in 10 cm × 10 cm beams increases with increasing TPR20,10 to reach a value of 1.0095 at TPR20,10 = 0.8 with a relative standard uncertainty of 0.4 %.

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Section: K Q Factors and Ratios Kcontrasting

confidence: 99%

Section: Introductionsupporting

confidence: 72%

Experimental determination ofk_Qfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Krauss

Kapsch

2014

Phys. Med. Biol.

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“…In small beams (2 cm × 2 cm) the thermal feedback between the core and the jacket has proven its interest when the jacket is not uniformly irradiated, leading to a relative uncertainty on the mean absorbed dose to core of about 0.18%. The results of the measurements with the GR-10 graphite calorimeter in the 2 cm × 2 cm size in the frame of the JRP7 project have been reported during this symposium [12] and will be the subject of another publication.…”

Section: Discussionmentioning

confidence: 95%

Small section graphite calorimeter (GR-10) at LNE-LNHB for measurements in small beams for IMRT

Daures¹,

Ostrowsky²,

Rapp

2012

Metrologia

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Within the Euramet JRP7 project External Beam Cancer Therapy, a work package was dedicated to the primary standards for IMRT (intensity modulated radiation therapy). The French national metrology laboratory for ionizing radiations, LNE-LNHB, was involved in determining absorbed dose to water based on graphite calorimeters in 6 MV and 12 MV beams for field sizes of 10 cm × 10 cm, 4 cm × 4 cm and 2 cm × 2 cm. The existing GR-09 graphite calorimeter has been successfully used for the beam sizes of 10 cm × 10 cm and 4 cm × 4 cm whereas it was not small enough to perform measurements in the 2 cm × 2 cm beam size. Therefore, during the project a small section graphite calorimeter, GR-10, has been developed. This work deals with the design, construction and tests of this new graphite calorimeter.

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“…Thus, the vials were placed one by one in a 30 × 30 × 30 cm 3 water tank, their geometrical center at 10 cm depth and their longitudinal axis perpendicular to the beam axis (figure 1(a)). The absorbed dose to water values are directly traceable to the French national references based on calorimetry primary measurements [33].…”

Section: Specific Irradiation and Reading Conditions For The Studiesmentioning

confidence: 99%

Preliminary dosimetric characterization of EDBreast gel

Stien

Rousseau

Bordy

et al. 2023

Biomed. Phys. Eng. Express

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Purpose: EDBreast gel is an alternative Fricke gel dosimeter, read by Magnetic Resonance Imaging, in which sucrose is added to lower diffusion effects. This paper aims at determining the dosimetric characteristics of this dosimeter.Methods: The characterization has been performed in high energy photon beams. The dose-response of the gel has been evaluated as well as its detection limit, its fading effects, the reproducibility of its response and its stability over time. Its energy and dose-rate dependence has been investigated, and the overall dose uncertainty budget established. Once characterized, the dosimetry method has been applied to a simple reference irradiation case in a 6 MV photon beam, with the measurement of the lateral dose profile of a 2 x 2 cm² field. The results have been compared with microDiamond measurements.Results: In addition to its low diffusivity, the gel presents a high sensitivity, no dose-rate dependence considering TPR(20-10) values ranging from 0.66 to 0.79 and an energy response comparable to ionization chambers. However, its non-linear dose-response induces a high uncertainty on the measured dose (8 % (k=1) at 20 Gy) and reproducibility issues. The profile measurements displayed discrepancies compared to the microDiamond due to diffusion effects. The appropriate spatial resolution was estimated using the diffusion coefficient. Conclusion: EDBreast gel dosimeter presents interesting characteristics for applications in clinics, but the linearity of its dose-response should be improved to lower the uncertainties and to enhance the reproducibility.

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New standards of absorbed dose to water under reference conditions by graphite calorimetry for⁶⁰Co and high-energy x-rays at LNE-LNHB

Cited by 10 publications

References 50 publications

Experimental determination ofk_Qfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Experimental determination ofk_Qfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Small section graphite calorimeter (GR-10) at LNE-LNHB for measurements in small beams for IMRT

Preliminary dosimetric characterization of EDBreast gel

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New standards of absorbed dose to water under reference conditions by graphite calorimetry for60Co and high-energy x-rays at LNE-LNHB

Cited by 10 publications

References 50 publications

Experimental determination ofkQfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Experimental determination ofkQfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Small section graphite calorimeter (GR-10) at LNE-LNHB for measurements in small beams for IMRT

Preliminary dosimetric characterization of EDBreast gel

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New standards of absorbed dose to water under reference conditions by graphite calorimetry for⁶⁰Co and high-energy x-rays at LNE-LNHB

Experimental determination ofk_Qfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV

Experimental determination ofk_Qfactors for cylindrical ionization chambers in 10 cm × 10 cm and 3 cm × 3 cm photon beams from 4 MV to 25 MV