DIFFUSION OF FERRIC IONS IN AGAROSE DOSIMETER GELS

The diffusion of ferric ions produced by irradiation in a dosimeter gel, consisting of a ferrous sulphate solution and agarose gel, has been studied. The diffusion coefficient of ferric ions in the gel was found to be 1.91 x 10(-2) cm2 h-1 +/-5%. It was shown that the dose image obtained with an MR scanner deteriorates due to diffusion. This deterioration can be predicted with the aid of the measured diffusion coefficient. It was concluded that if the MR measurements (1/T1 image) of a typical depth-dose distribution are carried out within 2 hours of irradiation the diffusion will not have a significant effect on the results.