Validation of MR-based polymer gel dosimetry as a preclinical three-dimensional verification tool in conformal radiotherapy

The aim of this work was to investigate MR-based polymer gel dosimetry as a three-dimensional (3D) dosimetry technique in conformal radiotherapy. A cy lindrical container filled with polymer gel was placed in a water-filled to rso phantom to verify a treatment plan for the conformal irradiation of a m ediastinal tumor located near the esophagus, Magnetic resonance spin-spin r elaxation rate images were acquired and, after calibration, converted to ab sorbed dose distributions. The dose maps were compared with dose distributi ons measured using radiographic film. The average root-mean-square structur al deviation, for the complete dose distribution, amounted to less than 3% between gel and film dose maps. It may be expected that MR gel dosimetry wi ll become a valuable tool in the verification of 3D dose distributions. The influence of imaging artifacts arising from eddy currents, temperature dri ft during scanning, and B1 field inhomogeneity on the dose maps was taken i nto account and minimized. Magn Reson Med 43:116-125, 2000, (C) 2000 Wiley- Liss, Inc.