From the limits of the classical model of sensitometric curves to a realistic model based on the percolation theory for GafChromic™ EBT films

Moral, F. del; Ferrero, Jenny; Willisch, P.; Ramírez, R. D.; Teijeiro, A.; Medina, Antonio López; Andrade, Bárbara; Vazquez, Julio; Salvador, Francisco; Medal, D.; Salgado, Manuel; Muñoz, Víctor Mario Aguirre

doi:10.1118/1.3187226

Cited by 20 publications

(33 citation statements)

References 54 publications

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“…Equation implies that the concentration increases with dose and saturates reaching a maximum value

C_{p}

, which can be interpret as the total concentration of centers in which a PDA of color phase “ p ” can grow. The rate at which the polymer concentration increases is given by

{italicσ}_{p} α

, where

σ_{p}

represents the interaction cross section associated to creating a polymer of color phase p upon interaction of ionizing radiation with a polymerizable center, and α is a proportionality constant relating the dose to the charged particle fluence,

α = false(1.37 \pm 0.13 false) \times 10^{9}

^{- 2}

^{- 1}

. Furthermore, Eq.…”

Section: Methodsmentioning

confidence: 99%

“…Similarly, for the optimization of the calibration curve, a series of improvements have been put forward. There is a tendency to describe the calibration, or dose–response curve, by a phenomenological model instead of an empirical parametrization using for instance polynomial fits …”

Section: Introductionmentioning

confidence: 99%

“…The simple single‐hit model however fails to describe the observed dose–response of the films with the precision and accuracy required for IMRT. del Moral et al revised and improved the theoretical model by taking into account that not all active centers have the same interaction cross section. As the interaction cross section is proportional to the size of the active centers, it is necessary to average over the distribution of active centers.…”

Section: Introductionmentioning

confidence: 99%

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Modeling the dose dependence of the vis-absorption spectrum of EBT3 GafChromic™ films

et al. 2017

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Purpose: The aim of this work was to model the dose dependence of the darkening of GafChromic TM EBT3 films by combining the optical properties of the polydiacetylene polymer phases, and a modified version of the single-hit model, which will take the stick-like shape of the monomer microcrystals into account. Second, a comparison is made between the quantification of the film darkening by flatbed scanning and by UV-vis absorption spectroscopy. Method: GafChromic TM EBT3 films were irradiated with a 6 MV photon beam at dose levels between 0 and 50 Gy. The radiation-induced darkening of the films is quantified by a flatbed scanner, and by UV-vis absorption spectroscopy in the wavelength range of 220-750 nm. From the UV-vis absorption spectra, the contribution of each polymer phase to the absorbance was deduced. Next, the dose dependence of the polymer content is described by a modified single-hit model where the size distribution of polymerizable centers is approximated by way of the size distribution of the monomer microcrystals in the film. Results: The absorption properties of the film can be accurately quantified by UV-vis spectroscopy for dose levels between 0 and 10 Gy. Over 10 Gy, the absorption spectrum saturates due to the limited sensitivity of the spectrometer. The modified single-hit model was successful in describing the increasing polymer concentration with radiation dose, using a log-normal distribution for the length of the stick-like monomer microcrystals. The dose dependence of the polymer content, deduced from the UV-vis absorption spectrum, differs from that of the flatbed scanning method and is more sensitive to changes in dose. Conclusion: The dose dependence of the polymer concentration can be modeled by taking into account the distribution of active centers using the microstructure of the active layer for dose levels between 0 and 10 Gy. The dissimilar dose dependence of the polymer concentration and the absorbance must be accounted for when modeling darkening from the kinetics of the photopolymerization reaction.

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“…Equation implies that the concentration increases with dose and saturates reaching a maximum value

C_{p}

, which can be interpret as the total concentration of centers in which a PDA of color phase “ p ” can grow. The rate at which the polymer concentration increases is given by

{italicσ}_{p} α

, where

σ_{p}

α = false(1.37 \pm 0.13 false) \times 10^{9}

^{- 2}

^{- 1}

. Furthermore, Eq.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling the dose dependence of the vis-absorption spectrum of EBT3 GafChromic™ films

et al. 2017

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“…For complete treatment of the two models discussed here, the reader is referred to the work of del Moral et al 32 The single-hit and percolation models are based on the theory that film response arises from interactions between energetic quanta and active film elements. Slight rearrangement and relabeling of the variables in Eq.…”

Section: C1 Theoretical Response Modelsmentioning

confidence: 99%

“…Slight rearrangement and relabeling of the variables in Eq. (14) of the work of del Moral et al 32 yields the net change in OD (netOD) predicted by the single-hit model and is given by…”

Section: C1 Theoretical Response Modelsmentioning

confidence: 99%

A prototype, glassless densitometer traceable to primary optical standards for quantitative radiochromic film dosimetry

et al. 2015

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A new analytical model for the response curve in megavoltage photon beams of the radiochromic EBT3 films measured with flatbed scanners

Rodríguez

Garcia-Pinto

Martínez

et al. 2022

J Applied Clin Med Phys

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The aim of this work is to study a new analytical model which describes the dose-response curve in megavoltage photon beams of the radiochromic EBT3 film measured with two commercially available flatbed scanners. This model takes into account the different increase of the number of two types of absorbents in the film with absorbed dose and it allows to identify parameters that depend on the flatbed scanner and the film model, and parameters that exclusively depend on the production lot. In addition, the new model is also compared with other models commonly used in the literature in terms of its performance in reducing systematic calibration uncertainties. Methods and materials:The new analytical model consists on a linear combination of two saturating exponential functions for every color channel. The exponents modeling the growing of each kind of absorbent are film model and scanner model-dependent, but they do not depend on the manufacturing lot. The proposed model considers the different dose kinetics of each absorbent and the apparent effective behavior of one of the absorbents in the red color channel of the scanner. The dose-response curve has been measured using EBT3 films, a percentage depth dose (PDD) calibration method in a dose range between 0.5 and 25 Gy, and two flatbed scanners: a Microtek 1000 XL and an EPSON 11000 XL. The PDD calibration method allows to obtain a dense collection of calibration points which have been fitted to the proposed response curve model and to other published models. The fit residuals were used to evaluate the performance of each model compared with the new analytical model. Results:The model presented here does not introduce any systematic deviations up to the degree of accuracy reached in this work. The residual distribution is normally shaped and with lower variance than the distributions of the other published models. The model separates the parameters reflecting specific characteristics of the dosimetry system from the linear parameters which depend only on the production lot and are related to the relative abundance of each type of absorbent. The calibration uncertainty is reduced by a mean factor of two by using this model compared with the other studied models.

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From the limits of the classical model of sensitometric curves to a realistic model based on the percolation theory for GafChromic™ EBT films

Abstract: The percolation model fulfills the accuracy requirements for quality-control procedures when large ranges of doses are used and offers a physical explanation for the film response.

Cited by 20 publications

References 54 publications

Modeling the dose dependence of the vis-absorption spectrum of EBT3 GafChromic™ films

Modeling the dose dependence of the vis-absorption spectrum of EBT3 GafChromic™ films

A prototype, glassless densitometer traceable to primary optical standards for quantitative radiochromic film dosimetry

A new analytical model for the response curve in megavoltage photon beams of the radiochromic EBT3 films measured with flatbed scanners

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