Absorbed dose distribution measurements in brachytherapy using ferrous sulphate gel and magnetic resonance imaging.

Measurements of spatial dose distribution by means of Fricke gel dosimetry and magnetic resonance imaging (MRI) are reported for two different brachytherapy applications: a configuration of three parallel linear high dose-rate (HDR) microSelectron 192Ir source trains and a low dose-rate (LDR) 106Ru eye applicator. The presented results verify that sufficient radiation induced change in spin-lattice relaxation time (T1) is obtained within the gel dosimeter to achieve satisfactory resolution for both the HDR 192Ir source train and the LDR 106Ru applicator. Satisfactory spatial resolution is also obtained, so that the large dose gradients of the brachytherapy sources can be visualized by MRI of irradiated dosimetry gels. A reliable representation of the relative dose level is achieved by calculated T1 images. The presented study supports the use of dose distribution measurements by means of gel dosimetry and MRI in complex brachytherapy applications.