Study of polymerization growth uniformity in polymer gel dosimeter

Abstract

In this work, the spatial uniformity of the polymerization growth of the MAGIC gel in the case of an internal irradiation with iodine-131 was studied. A compartmental mathematical model taking into account the kinetics of polymerization of the MAGIC gel was developed and validated by experimental measurements. In order to check the radioactivity homogeneity distribution in the samples, we performed their scintigraphy, while- in order to study the rate of polymerization- we measured the intensity of the MRI signal emitted by each of the samples. The wide dispersion in signal strength observed between different regions of the same sample indicates that the value of the relaxation time T2 varies from one point to another. Scintigraphy and MRI images showed that a homogeneous distribution of 131I activity does not necessarily imply isotropic polymerization. The phenomenon is probably due to the fact that iodine-131 emits beta particles with different energies and the length of polymers does not increase with the same speed for all the polymers in formation. On this basis, we have established a mathematical model which compartmentalizes different species of protons which participate in the modification of the MRI signal.