Monte‐Carlo calculation of output correction factors for ionization chambers, solid‐state detectors, and EBT3 film in small fields of high‐energy photons

Климанов, В. А.; Kirpichev, Yury S.; Serikbekova, Zarina K.; Белоусов, А. В.; Krusanov, G. A.; Walwyn‐Salas, Gonzalo; Морозов, В. Н.; Колыванова, М. А.

doi:10.1002/acm2.13753

Cited by 3 publications

(5 citation statements)

References 54 publications

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“…For the scintillator Exradin W2 1x1 and the microDiamond, the data of the two smallest fields was not considered in the fit due to the incompatibility with the fit model. For comparison also 18 MV data of the microDiamond 60019 from Klimanov et al 25 . is presented.…”

Section: Resultsmentioning

confidence: 99%

“…However, there are individual reports on output correction for EBT3 film. Klimanov et al 25 . calculated corrections up to 2% for a field size of 0.5 cm using Monte Carlo simulations.…”

Section: Methodsmentioning

confidence: 99%

“…Film shows water-equivalent response consistent with Monte Carlo simulations for nominal field sizes down to 0.5 cm, for a wide energy range in the MV regime.However,there are individual reports on output correction for EBT3 film. Klimanov et al 25 calculated corrections up to 2% for a field size of 0.5 cm using Monte Carlo simulations. Their data show high uncertainties and large fluctuations (up to 2 %) throughout the energies with no clear energy trend.…”

Section: Field Output Correction Factorsmentioning

confidence: 99%

“…For PinPoint 3D, Razor Chamber and Razor Nano Chamber data, the data of the two smallest fields was not considered in the fit due to the incompatibility with the fit model. For comparison also 18 MV data of the Semiflex 31021 from Klimanov et al 25 is presented. k f clin ,f msr Q clin ,Q msr (s) = 1 within their uncertainties, whereas the Exradin W2 1x3 detector over-responded up to 4% at a field size of s = 0.7 cm.…”

Section: Scintillatorsmentioning

confidence: 99%

“…On the other hand, the PinPoint 3D showed a slightly lower under-response at smaller field sizes at 18 MV than for 10 MV. For the Semiflex 31021 and the microDiamond 60019 Klimanov et al 25 determined correction factors for energies between 10 and 20 MV including 18 MV using Monte Carlo simulations. For the Semiflex 31021 the factors match within their uncertainties (Figure 6), for the microDiamond they do not (Figure 3).…”

Section: Comparison To Lower Energy Datamentioning

confidence: 99%

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Small field output correction factors at 18 MV

Ringholz,

Sauer,

Wegener

2023

Medical Physics

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BackgroundThe response of various detectors in the radiotherapy energy range has been investigated, especially for 6 and 10 MV energies for small fields, and is summarized in TRS‐483. However, data for accelerator energies above 10 MV are sparse or unavailable for many detectors, especially for the energy of 18 MV. Small variations in field output factors for the commissioning of a treatment planning system can have a high impact on calculation of dose distributions.PurposeMany studies describe an energy dependence of the response for a large number of detectors. We wanted to close the gap for the 18 MV energy regime and determined field output correction factors for different detectors at 18 MV.MethodsAn ELEKTA Versa HD accelerator at 18 MV was used together with a PTW MP3 water phantom at an SSD of 90 cm. The following detectors were examined: PTW Semiflex 31021, PinPoint 3D 31022, diode 60012, diode 60008 and microDiamond 60019, Sun Nuclear EDGE detector, IBA PFD, SFD, Razor Chamber, Razor Nano Chamber and Razor Diode, Standard Imaging Scintillator Exradin W2 1x3, W2 1x1 and Gafchromic EBT3 film. The dose response was determined at a depth of 10 cm for square fields between 0.5 and 10 cm side length. As reference data a composure of radiochromic film data for small fields ( cm) and data of all compatible chambers for larger fields ( cm) was used. The effective field sizes of small fields were determined from profiles obtained on radiochromic film. The obtained field output correction factors obey the rules of the TRS‐483 protocol.ResultsThe W2 1x1 scintillator and the Razor Chamber showed the smallest deviations from the reference curve. The shielded diodes (diode 60008, EDGE detector) showed the highest over‐response at small fields, followed by PFD, microDiamond and the unshielded diodes (diode 60012, SFD). The ionization chambers exhibited the well‐known volume effect, that is, strong under‐response at small fields of up to 9% for the PinPoint 3D, 7% for the Razor Chamber and up to 30% for the Semiflex detector for the smallest studied field size. The small chambers showed a polarity effect in axial orientation, especially the Razor Nano Chamber. Corrections at 18 MV are generally larger than those provided by TRS‐483, continuing the trend of increasing corrections between 6 and 10 MV also at a higher accelerator energy. Only the PinPoint 3D Chamber showed a slightly smaller correction.ConclusionsField output correction factors were determined for square field sizes between 0.5 and 10 cm at 18 MV. Most detectors needed a larger correction than at 6 and 10 MV. Thus, the use of correction factors will improve beam data for 18 MV.

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Section: Resultsmentioning

confidence: 99%

“…However, there are individual reports on output correction for EBT3 film. Klimanov et al 25 . calculated corrections up to 2% for a field size of 0.5 cm using Monte Carlo simulations.…”

Section: Methodsmentioning

confidence: 99%

Section: Field Output Correction Factorsmentioning

confidence: 99%

Section: Scintillatorsmentioning

confidence: 99%

Section: Comparison To Lower Energy Datamentioning

confidence: 99%

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Small field output correction factors at 18 MV

Ringholz,

Sauer,

Wegener

2023

Medical Physics

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Monte‐Carlo calculation of output correction factors for ionization chambers, solid‐state detectors, and EBT3 film in small fields of high‐energy photons

Климанов

Kirpichev²,

Serikbekova

et al. 2022

J Applied Clin Med Phys

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High‐energy accelerators are often used in oncological practice, but the information on the small‐field dosimetry for the photon beams with nominal energy above 10 MV is limited. The goal of the present work was to determine the values of the output correction factor ( ) for solid‐state detectors (Diode E, PTW 60017; microDiamond, PTW 60019), EBT3 film, and ionization chambers (Semiflex, PTW 31010; Semiflex 3D, PTW 31021; PinPoint, PTW 31015; PinPoint 3D, PTW 31016) in the small fields formed by 10, 15, 18, and 20 MV photon beams. The output correction factors were calculated by Monte‐Carlo method using EGSnrc toolkit for six field sizes (from to ) for isocentric and constant source‐to‐surface distance (SSD) techniques. The decrease in the field size led to an increase in for ionization chambers, while for solid‐state detectors and radiochromic film, were less than unity at the smallest field size. A larger sensitive volume of ionization chamber corresponded to a stronger deviation of output correction factor from unity: 1.847 (125 mm 3 PTW 31010) versus up to 1.183 (16 mm 3 PTW 31016) at the smallest field of 10 MV beam. The calculated output correction factors were used to correct the output factors for PTW 60017, PTW 60019, and EBT3. The deviation of the corrected output factor from the results of Monte‐Carlo simulation did not exceed 3% in the fields from to for 10 and 18 MV beams. Thus, Diode E, microDiamond, and EBT3 film can be recommended for small‐field dosimetry of high‐energy photons.

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