Dose response characteristics and basic dose distribution data for a polymerization-based dosemeter gel evaluated using MR.

A safe and reproducible mixing procedure for the manufacture of a polymerization-based dosemeter gel evaluated using MRI (PoMRI) is presented. The dose response, obtained by irradiating gel-filled vials with absorbed doses in the interval 0-20 Gy and evaluated with respect to 1/T2, was found to be linear in the interval 0-8 Gy, with a sensitivity of 0.211 s-1Gy-1 (r2 = 0.998) at 1.5 T. Evaluation of the same set of vials with respect to 1/T1 gave a sensitivity of 0.018 s-1Gy-1 (r2 = 0.960). PoMRI and diode data were compared for standard photon and electron treatment beams. A deviation of less than 3% was found between the two methods for central depth dose curves as well as dose profiles (2 mm for electrons in the steep dose gradient regions). The importance of the method used for background correction for the reliability of the results was also evaluated. Barex (with a wall thickness of 1.5 mm) was investigated for use as phantom material and found to be favourable compared with glass. The results obtained in this study show that PoMRI has excellent potential as a 3D detector.