Dose rate dependency of micelle leucodye 3D gel dosimeters

Vandecasteele, J; Ghysel, S; Deene, Yves De

doi:10.1088/1742-6596/250/1/012009

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…These dosimeters exhibit less toxicity, ease of preparation, water equivalence, and a satisfactory precision in 3D dosimetry. However, they are characterized by relatively low dose sensitivity and, depending on the dye used and their composition, their dose response can be sensitive to environmental factors or the dose rate (Vandecasteele et al 2010, Nasr et al 2013, Nasr et al 2015b.…”

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confidence: 99%

Leuco crystal violet-Pluronic F-127 3D radiochromic gel dosimeter

et al. 2019

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This work reports results related to the manufacturing and optimisation of a leuco crystal violet (LCV)-Pluronic F-127 radiochromic gel dosimeter suitable for 3D radiotherapy dosimetry. A feature of this gel is that the natural gelatine polymer, which is most often used as a matrix in 3D dosimeters, is substituted with Pluronic F-127 synthetic copolymer (poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide). Pluronic F-127 ensures a higher transparency than gelatine, which may be beneficial for optical computed tomography readout, and improves the thermal properties in the temperature range above ~30 °C at which the gelatine physical gel converts to a solution. The optimal composition obtained comprises 2 mM LCV, 4 mM 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100), 17 mM trichloroacetic acid (TCAA) and 25% Pluronic F-127. Its main dose-response features are 4‒150 Gy linear dose range (150 Gy was the maximal dose applied to gels in this work), 0.0070 Gy−1 cm−1 dose sensitivity (derived from absorbance (600 nm) = f (dose) for 6 MeV electrons, 0.88(3) Gy s−1 and 0.0156 Gy−1 cm−1 derived from optical density (Δµ) = f (dose) for 6 MV x-rays, 0.1010 Gy s−1), low initial colour (initial absorbance = 0.0429) and a diffusion coefficient of crystal violet (CV) in LCV-Pluronic of 0.054 ± 0.023 mm2 h−1. Raman spectroscopy was used to characterize LCV-Pluronic chemical changes after irradiation. Differential scanning calorimetry (DSC) revealed that LCV-Pluronic is stable in temperatures between approximately 11 °C and 56 °C. Irradiation of LCV-Pluronic gel impacts on its first sol-gel transition temperature and the thermal effect of this process—both increased with absorbed dose, which might be related to the degradation of Pluronic. LCV-Pluronic is a promising 3D dosimeter for ionising radiation applications. Further work is needed to improve LCV-Pluronic response in the low dose region, and characterize potential effects of pH, temperature during irradiation, and radiation quality/dose rate on dose response characteristics.

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confidence: 99%

Leuco crystal violet-Pluronic F-127 3D radiochromic gel dosimeter

et al. 2019

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“…However, the model presented in this study has two main limitations: 1) Due to the dose-rate dependency, several dosimeters are required to parametrize the correction model. To date, all chemical dosimeters present a dose-rate dependency to some degree [1] , [9] , [10] , [11] . However, if the dependency could be reduced to an acceptable level in the clinical dose-rate range for protons, a correction model could potentially be established using a dosimeter irradiated with a single proton beam.…”

Section: Discussionmentioning

confidence: 99%

“…However, the clinical use of 3D dosimetry in PT is challenged by steep dose gradients and regions of high linear-energy-transfer (LET) [6] , [7] , [8] . Dose-rate dependency has also been observed for a variety of systems, but there is so far limited data for the dose-rate ranges pertinent to spot-scanning PT [1] , [9] , [10] , [11] .…”

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confidence: 99%

Empirical quenching correction in radiochromic silicone-based three-dimensional dosimetry of spot-scanning proton therapy

Valdetaro

Høye

Skyt

et al. 2021

Physics and Imaging in Radiation Oncology

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Background and purpose: Three-dimensional dosimetry of proton therapy (PT) with chemical dosimeters is challenged by signal quenching, which is a lower dose-response in regions with high ionization density due to high linear-energy-transfer (LET) and dose-rate. This study aimed to assess the viability of an empirical correction model for 3D radiochromic silicone-based dosimeters irradiated with spot-scanning PT, by parametrizing its LET and dose-rate dependency. Materials and methods: Ten cylindrical radiochromic dosimeters (Ø50 and Ø75 mm) were produced in-house, and irradiated with different spot-scanning proton beam configurations and machine-set dose rates ranging from 56 to 145 Gy/min. Beams with incident energies of 75, 95 and 120 MeV, a spread-out Bragg peak and a plan optimized to an irregular target volume were included. Five of the dosimeters, irradiated with 120 MeV beams, were used to estimate the quenching correction factors. Monte Carlo simulations were used to obtain dose and dose-averaged-LET (LET d ) maps. Additionally, a local dose-rate map was estimated, using the simulated dose maps and the machine-set dose-rate information retrieved from the irradiation log-files. Finally, the correction factor was estimated as a function of LET d and local dose-rate and tested on the different fields. Results: Gamma-pass-rates of the corrected measurements were >94% using a 3%-3 mm gamma analysis and >88% using 2%-2 mm, with a dose deviation of <5.6 ± 1.8%. Larger dosimeters showed a 20% systematic increase in dose-response, but the same quenching in signal when compared to the smaller dosimeters. Conclusion:The quenching correction model was valid for different dosimeter sizes to obtain relative dosimetric maps of complex dose distributions in PT.

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