Three-Dimensional Dosimetry Using Magnetic Resonance Imaging of Polymer Gel

Oh, Young Taek; Kang, Haejin; Kim, Miwha; Chun, Mison; Kang, Seung Hee; Suh, Chang Ok; Chu, Seong Sil; Seong, Jinsil; Kim, Gwi Eon

Abstract

PURPOSE: Three-dimensional radiation dosimetry using magnetic resonance imaging of polymer gel was recently introduced. This dosimetry system is based on radiation induced chain polymerization of acrylic monomers in a muscle equivalent gel and provide accurate 3 dimensional dose distribution. We planned this study to evaluate the clinical value of this 3-dimensional dosimetry.
MATERIALS AND METHODS
The polymer gel poured into a cylindrical glass flask and a spherical glass flask. The cylindrical test tubes were for dose response evaluation and the spherical flasks, which is comparable to the human head, were for isodose curves. T2 maps from MR images were calculated using software, IDL. Dose distributions have been displayed for dosimetry. The same spherical flask of gel and the same irradiation technique was used for film and TLD dosimetry and compared with each other.
RESULTS
The R2 of the gel respond linearly with radiation doses in the range of 2 to 15 Gy. The repeated dosimetry of spherical gel showed the same isodose curves. These isodose curves were identical to dose distributions from treatment planning system especially high dose range. In addition, the gel dosimetry system showed comparable or superior results with the film and TLD dosimetry.
CONCLUSION
The 3-dimensional dosimetry for conformal radiation therapy using MRI of polymer gel showed stable and accurate results. Although more studies are needed for convenient clinical application, it appears to be a useful tool for conformal radiation therapy.