MR Imaged Polymer Gel Radiation Dosimetry: Disclosed Yet Unpatented

The advent of complex radiotherapy techniques has created new challenges for radiation dosimetry. Intensity modulated, stereotactic, conformal radiotherapy, radiosurgery and brachytherapy present a field where both spatial and quantitative accuracy become crucial to the success of the treatment. Methods for true 3-D dosimetry are mostly based on various forms of chemical dosimetry such as Fricke dosimetry and the radiation-induced polymerization in solutions of monomers. The 3-D spatial information in these methods is preserved by embedding the radiosensitive chemicals in gel matrices which provide the necessary spatial stability of the dosimeter. The chemical changes in each of these dosimeters are measured by the NMR relaxation characteristics of it (longitudinal or transverse MR relaxation rate R1, R2) which are proportional to its absorbed dose. Advances in the chemical composition of the gels alleviated many irradiation, calibration and measurement uncertainties. Furthermore, advances in MRI technology lead to a more robust and reliable measurement method for 3-D polymer gel dosimetry. It is the scope of this work to present a roadmap, of the progress made thus far in MR imaged polymer gel dosimetry and offer a discussion for the reasons that such a large part of this progress had been disclosed yet unpatented.