Three-dimensional polymer gel dosimetry: basic physical properties of the dosimeter

This study concentrated on assessment of the basic physical properties of a polymer gel dosimeter evaluated by NMR. For this, BANG-2 type polymer gel was prepared. The dosimeters were irradiated by Co-60 gamma photons and by 4, 6 and 18 MV X-ray photons for doses in the range 0-50 Gy. The multi-echo CPMG sequence was used for the evaluation of T-2-relaxation times in the i rradiated gel dosimeters. Dependence of 1/T-2 in terms of the following fac tors was studied: absorbed dose, energy of applied radiation, temperature d uring NMR evaluation, time between irradiation and NMR evaluation and stren gth of the magnetic field. An exponential dependence of the 1/T-2 response on absorbed dose in the range 0-50 Gy was observed, while in the range 0-10 Gy the data could be fitted by a linear function. This paper also describe s the dependence of 1/T-2 response on: radiation energy, strength of magnet ic field and time from irradiation of the dosimeters to NMR evaluation. Inc rease of gel dosimeter 1/T-2 response with the decrease of the temperature during NMR evaluation has been qantitatively described. The polymer gel dos imetry system used in this study proved that it is a reliable system for th ree-dimensional dose distribution measurement. (C) 2001 Elsevier Science Lt d. All rights reserved.