13C-NMR,1H-NMR, and FT-Raman study of radiation-induced modifications in radiation dosimetry polymer gels

Queensland University of Technology, Brisbane, Queensland, Australia
Journal of Applied Polymer Science (Impact Factor: 1.77). 02/2001; 79(9):1572-1581. DOI: 10.1002/1097-4628(20010228)79:93.0.CO;2-B


1H- and 13C-NMR spectroscopy and FT-Raman spectroscopy are used to investigate the properties of a polymer gel dosimeter post-irradiation. The polymer gel (PAG) is composed of acrylamide, N,N′-methylene-bisacrylamide, gelatin, and water. The formation of a polyacrylamide network within the gelatin matrix follows a dose dependence nonlinearly correlated to the disappearance of the double bonds from the dissolved monomers within the absorbed dose range of 0–50 Gy. The signal from the gelatin remains constant with irradiation. We show that the NMR spin–spin relaxation times (T2) of PAGs irradiated to up to 50 Gy measured in a NMR spectrometer and a clinical magnetic resonance imaging scanner can be modeled using the spectroscopic intensity of the growing polymer network. More specifically, we show that the nonlinear T2 dependence against dose can be understood in terms of the fraction of protons in three different proton pools. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1572–1581, 2001

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Available from: Clive Baldock, Jul 09, 2014
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    • "From table 4 it can be seen that the dose sensitivity of the different monomers is influenced by the functional group. The functional group determines both the polymerization rate of the monomers (inversely related to the half-dose value D 1/2 (Lepage et al 2001d)) and the efficiency of cross-relaxation. The hydroxyl and amino groups serve as hydrogen bonding sites (Ceckler et al 1992). "
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    ABSTRACT: Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.
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    • "In the plot, the finger phantom extinction coefficients appear to saturate with increasing turbidity ( > ∼0.5 cm −1 ), but the onset of this effect is not observed in the spectroscopic data from 1 cm cuvettes until much higher turbidity ( > ∼1.2 cm −1 ). Had these experiments been conducted with irradiated polymer gels alone, saturation of the extinction coefficient in the phantom might have been misinterpreted as evidence of radiation-induced polymerization saturation (Lepage et al 2001). However, in this phantom, turbidity is the result of addition of the antiseptic. "
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    ABSTRACT: There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the gel. In this paper, we present the initial results of using an optical CT scanner to evaluate a novel phantom in which radiation-exposed polymer gels are simulated by the addition of colloidal suspensions of varying turbidity. The phantom may be useful as a calibration transfer standard for polymer gel dosimeters. The tests reveal some phenomena peculiar to light-scattering gels that need to be taken into account when calibrating polymer gel dosimeters.
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    • "). More recently, FT-Raman spectroscopy has been used in the direct monitoring of monomer consumption and polymer formation in polymer gel dosimeters [19] [20] [13]. Baldock et al were the first to illustrate the use of FT-Raman spectroscopy for the study of monomer consumption in irradiated polymer gel dosimeters. "
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