Evaluation of two calibration methods for MRI-based polymer gel dosimetry

Natanasabapathi, Gopishankar; Warmington, L; Watanabe, Yoichi

doi:10.1016/j.apradiso.2021.109754

Cited by 4 publications

(1 citation statement)

References 25 publications

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“…New investigations of polymeric formulations were proposed, such as the MAGAT (Methacrylic Acid Gelatin And Tetrakis (hydroxymethyl) phosphonium chloride), also composed of a gel matrix made of water and gelatin and some monomers. Some investigations have reported its characteristics as tissue-equivalent highest dosimeter sensitivity [20,21,[27][28][29], improving better than MAGIC polymer gels [22,30].…”

Section: Introductionmentioning

confidence: 99%

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

2022

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The present work compared the relative absorbed dose of some dosimetric materials, for energies of 250 kV and 6 MV, using PENELOPE and MNCPX codes. The composition of each material GD-301, TLD-100, MAGIC, and MAGAT were simulated and disposed of in a phantom filled with water following reference conditions recommended by the TRS-398 protocol. Percentage depth dose was used as a parameter of comparison. Since the obtained results with both codes were found a maximum difference of up to 2 % when compared the water material with experimental data before 6cm were found to a maximum difference of up to 2.2% for 6 MV and 5.5 % for 250 kV. Ratios between simulated PPD and experimental PDD values showed a maximum difference in the build-up region, for 6 MV, due to highsensitivityive from the incident fluency in the simulated and experimental conditions. The ratios for 250 kV showed significant differences from the simulated solid-state rather than gel dosimeters, due to its low energy, depth angular dependence from the solid-state dosimeter, as corroborating by literature. Even the differences showed for both codes, especially for lower energy, due to cross-the section database that implied the interaction probability for each Monte Carlo code, this method has been widely used to model radiation transport in several applications in medical physics, especially in dosimetry.

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Section: Introductionmentioning

confidence: 99%

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

2022

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Validation of complex radiotherapy techniques using polymer gel dosimetry

Karger,

Elter,

Dorsch

et al. 2024

Phys. Med. Biol.

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Modern radiotherapy delivers highly conformal dose distributions to irregularly shaped target volumes while sparing the surrounding normal tissue. Due to the complex planning and delivery techniques, dose verification and validation of the whole treatment workflow by end-to-end tests became much more important and polymer gel dosimeters are one of the few possibilities to capture the delivered dose distribution in 3D. The basic principles and formulations of gel dosimetry and its evaluation methods are described and the available studies validating device-specific geometrical parameters as well as the dose delivery by advanced radiotherapy techniques, such as 3D-CRT/IMRT and SRS treatments, the treatment of moving targets, online-adaptive MRgRT as well as proton and ion beam treatments, are reviewed. The present status and limitations as well as future challenges of polymer gel dosimetry for the validation of complex radiotherapy techniques are discussed.

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Verification of dose distribution in high dose-rate brachytherapy for cervical cancer using a normoxic N-vinylpyrrolidone polymer gel dosimeter

Watanabe

Maeyama

Mizukami

et al. 2022

Journal of Radiation Research

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The polymer gel dosimeter has been proposed for use as a 3D dosimeter for complex dose distribution measurement of high dose-rate (HDR) brachytherapy. However, various shapes of catheter/applicator for sealed radioactive source transport used in clinical cases must be placed in the gel sample. The absorbed dose readout for the magnetic resonance (MR)-based polymer gel dosimeters requires calibration data for the dose-transverse relaxation rate (R2) response. In this study, we evaluated in detail the dose uncertainty and dose resolution of three calibration methods, the multi-sample and distance methods using the Ir-192 source and the linear accelerator (linac) method using 6MV X-rays. The use of Ir-192 sources increases dose uncertainty with steep dose gradients. We clarified that the uniformly irradiated gel sample improved the signal-to-noise ratio (SNR) due to the large slice thickness of MR images and could acquire an accurate calibration curve using the linac method. The curved tandem and ovoid applicator used for intracavitary irradiation of HDR brachytherapy for cervical cancer were reproduced with a glass tube to verify the dose distribution. The results of comparison with the treatment planning system (TPS) calculation by gamma analysis on the 3%/2 mm criterion were in good agreement with a gamma pass rate of 90%. In addition, the prescription dose could be evaluated accurately. We conclude that it is easy to place catheter/applicator in the polymer gel dosimeters, making them a useful tool for verifying the 3D dose distribution of HDR brachytherapy with accurate calibration methods.

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Evaluation of two calibration methods for MRI-based polymer gel dosimetry

Cited by 4 publications

References 25 publications

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

Validation of complex radiotherapy techniques using polymer gel dosimetry

Verification of dose distribution in high dose-rate brachytherapy for cervical cancer using a normoxic N-vinylpyrrolidone polymer gel dosimeter

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