Measurement of ferric ion diffusion coefficient in Fricke-infused agarose gel from MR image intensity changes

Due to its high sensitivity, superior tissue equivalence and three-dimensional characteristics, Fricke-infused gel has been used in various radiation dosimetry applications. However, its measurement accuracy has been seriously affected by ferric ion diffusion contamination. A mathematical modeling was adopted to calculate the ferric ion diffusion coefficient based on the radiation induced magnetic resonance (MR) image intensity change in Fricke-agarose gels. A fast magnetic resonance imaging acquisition technique was employed to avoid the smearing of acquired data due to diffusion over an extended period of time. Our results showed that for a Fricke-agarose gel which contained 1 mM ammonium ferrous sulfate, 1% agarose, 1 mM sodium chloride and 50 mM sulfuric acid, its ferric ion diffusion coefficient is 1.31 × 10^-2 cm² h^-1 at room temperature. This value falls within the 1 ∼ 2 × 10^-2 cm² h^-1 range obtained by previous studies under varying concentrations of gel ingredients.