Accuracy and efficiency of published film dosimetry techniques using a flat-bed scanner and EBT3 film

Spelleken, E.; Crowe, Scott; Sutherland, Bess; Challens, Cameron; Kairn, Tanya

doi:10.1007/s13246-018-0620-4

Cited by 14 publications

(15 citation statements)

References 21 publications

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“…45 It also should be understood that the simulated D Med,Q D Det,Q values in this study only correct for the material differences between film and lung, and do not account for other uncertainties involved with film dosimetry. 41,42,46 Measurements in lung phantoms, particularly of small fields, are becoming increasingly important as more departments attempt to commission or validate treatment planning system calculations for stereotactic ablative radiotherapy treatments of small lung lesions. 21,26,27 Film measurements in lung phantoms should be corrected using values in Tables I--III, as shown in Eq.…”

Section: Discussionmentioning

confidence: 99%

“…It also should be understood that the simulated

\frac{D_{M e d, Q}}{D_{D e t, Q}}

values in this study only correct for the material differences between film and lung, and do not account for other uncertainties involved with film dosimetry 41,42,46 …”

Section: Discussionmentioning

confidence: 99%

“…It should be noted that

D_{F i l m, Q}

in Eq. () is the final dose value obtained after applying the appropriate calibration and sensitivity correction factors (see e.g., 41,42 ).…”

Section: Methodsmentioning

confidence: 99%

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Technical Note: Small field dose correction factors for radiochromic film in lung phantoms

Charles¹,

Crowe

Kairn

2021

Medical Physics

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Purpose: Radiochromic film has been established as a detector that can be used without the need for perturbation correction factors for small field dosimetry in water. However, perturbation factors in low density media such as lung have yet to be published. This study calculated the factors required to account for the perturbation of radiochromic film when used for small field dosimetry in lung equivalent material. Method: Monte Carlo simulations were used to calculate dose to Gafchromic EBT3 film when placed inside a lung phantom. The beam simulated had a nominal energy of 6 MV and the field sizes simulated ranged from 10 × 10 mm 2 to 30 × 30 mm 2 . The lung density simulated was varied between 0.2 and 0.3 g/cm 3 . Each simulation was repeated with the film replaced by lung material (the same as the surrounding medium), and the required correction factors for film dosimetry in lung ( D Med,Q D Det,Q ) were calculated by dividing the dose in lung by the dose in film. Results: For field sizes 30 × 30 mm 2 and larger, no correction factors were required. At a 20 × 20 mm 2 field size, small corrections were required, but were within the approximate accuracy of film dosimetry (~2%). For a 10 × 10 mm 2 field size, significant correction factors need to be applied (0.935 for lung density of 0.20 g/cm 3 to 0.963 for lung density of 0.30 g/cm 3 ). The values lower than one mean that the film is over-responding. At the "upstream" lung-water interface the correction factors were close to unity; while at the downstream interface the corrections required were marginally smaller to those at the center of lung. One centimeter or more away from the interfaces, the correction factor did not vary as a function distance from the interface (in the beam direction). Away from the central axis (perpendicular to the beam direction), the correction factors increased slightly (away from unity) as a function of off-axis distance, before abruptly changing direction at the penumbra, with the film actually under-responding by~10% outside the field edges. Conclusion: Accurate dosimetry of very small fields (15 × 15 mm 2 or smaller) using radiochromic film requires correction factors for the perturbation of the film on the surrounding lung material. This correction factor was as high as 6.5% for a 10 × 10 mm 2 field size and a density of 0.2 g/cm 3 . This will increase if either the density or the field size decrease further. This correction factor does not vary as a function of depth in lung once charged particle equilibrium is established.

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Section: Discussionmentioning

confidence: 99%

“…It also should be understood that the simulated

\frac{D_{M e d, Q}}{D_{D e t, Q}}

values in this study only correct for the material differences between film and lung, and do not account for other uncertainties involved with film dosimetry 41,42,46 …”

Section: Discussionmentioning

confidence: 99%

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Technical Note: Small field dose correction factors for radiochromic film in lung phantoms

Charles¹,

Crowe

Kairn

2021

Medical Physics

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“…The films were scanned 24 h after irradiation using an Epson Perfection V800 Photo scanner (Epson, Suwa, Japan) in transmission mode with no color correction, 1200 dpi and 48 bit color. The Epson V800 scanner has previously been compared to the more commonly used Epson 10000XL 29 and shown to have 0.3% lower dose uncertainty but a stronger lateral response function, 0.2% over 8 cm and 2.7% less sensitivity on the relevant red channel 30 . The films were analyzed using the polynomial netOD method 31 taking the red channel, calculating the dose as where is the polynomial fit to the dose calibration curve and , are the red channel values of the EBT3 film pre- and post-irradiation.…”

Section: Methodsmentioning

confidence: 99%

A focused very high energy electron beam for fractionated stereotactic radiotherapy

Svendsen

Guénot

Svensson

et al. 2021

Sci Rep

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An electron beam of very high energy (50–250 MeV) can potentially produce a more favourable radiotherapy dose distribution compared to a state-of-the-art photon based radiotherapy technique. To produce an electron beam of sufficiently high energy to allow for a long penetration depth (several cm), very large accelerating structures are needed when using conventional radio-frequency technology, which may not be possible due to economical or spatial constraints. In this paper, we show transport and focusing of laser wakefield accelerated electron beams with a maximum energy of 160 MeV using electromagnetic quadrupole magnets in a point-to-point imaging configuration, yielding a spatial uncertainty of less than 0.1 mm, a total charge variation below $$1 \%$$ 1 % and a focal spot of $$2.3 \times 2.6\;{\text {mm}}^2$$ 2.3 × 2.6 mm 2 . The electron beam was focused to control the depth dose distribution and to improve the dose conformality inside a phantom of cast acrylic slabs and radiochromic film. The phantom was irradiated from 36 different angles to obtain a dose distribution mimicking a stereotactic radiotherapy treatment, with a peak fractional dose of 2.72 Gy and a total maximum dose of 65 Gy. This was achieved with realistic constraints, including 23 cm of propagation through air before any dose deposition in the phantom.

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“…Until today, the flatbed scanner [9,10,18,[23][24][25] and visible spectroscopy [7,8,17,21] are considered to be the most acceptable optical tools in analyzing the color changes of the radiochromic film and red channel/wavelength to be the most sensitive in the application. Hence, to utilize only a single red wavelength from a spectrometer or a single red channel from a scanner is not a cost-effective measure.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy and Light Emitting Diodes Based System in Characterizing External Beam Therapy 3 Films for Solar Ultraviolet Measurement

Shah

Omar

2019

Photonic Sens

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Gafchromic external beam therapy 3 (EBT3) film has widely been used in medical field applications. Principally, the EBT3 film's color gradually changes from light green to darker color under incremental exposures by ionizing or even non-ionizing ultraviolet (UV) radiation. Peak absorbance of the EBT3 film can be used to predict absorbed doses by the film. However, until today, related researches still rely on spectrometers for color analysis of EBT3 films. Hence, this paper presents a comparative analysis between results produced by the spectrometer and a much simpler light-emitting diode-photodiode based system in profiling the color changes of EBT3 films after exposure by solar UV radiation. This work has been conducted on a set of 50 EBT3 samples with incremental solar UV exposure (doses). The wavelength in the red region has the best sensitivity in profiling the color changes of EBT3 films for low solar UV exposure measurement. This study foresees the ability of blue wavelength to profile films with a large range of solar UV exposure. The LED (light emitting diode)-based optical system has produced comparable measurement accuracies to the spectrometer and thus, with a potential for replacing the need for a multipurpose spectroscopy system for simple measurement of light attenuation.

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Accuracy and efficiency of published film dosimetry techniques using a flat-bed scanner and EBT3 film

Cited by 14 publications

References 21 publications

Technical Note: Small field dose correction factors for radiochromic film in lung phantoms

Technical Note: Small field dose correction factors for radiochromic film in lung phantoms

A focused very high energy electron beam for fractionated stereotactic radiotherapy

Spectroscopy and Light Emitting Diodes Based System in Characterizing External Beam Therapy 3 Films for Solar Ultraviolet Measurement

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