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

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.