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

H-1- and C-13-NMR spectroscopy and FT-Raman spectroscopy are used to invest igate the properties of a polymer gel dosimeter post-irradiation. The polym er gel (PACT) is composed of acrylamide, N,N'-methylene-bisacrylamide, gela tin, and water. The formation of a polyacrylamide network within the gelati n matrix follows a dose dependence nonlinearly correlated to the disappeara nce of the double bonds from the dissolved monomers within the absorbed dos e range of 0-50 Gy. The signal from the gelatin remains constant with irrad iation. We show that the NMR spin-spin relaxation times (T-2) of PAGs irrad iated 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 nonlin ear T-2 dependence against dose can be understood in terms of the fraction of protons in three different proton pools. (C) 2000 John Wiley & Sons, Inc .