Three-Dimensional Gel Dosimetry for Dose Volume Histogram Verification in Stereotactic Radiosurgery

The purpose of this study was to test the capability of gel dosimetry to measure dose volume histograms (DVHs) for stereotactic radiosurgery and stereotactic radiosurgery/radiotherapy applications. A custom-made head phantom able to accommodate a flask with polymer gel was used to measure DVHs for different irradiation geometries on the Leksell Gamma Knife (R) and BrainLAB stereotactic system installed on a linear accelerator Varian Clinac 2100 C/D. A polymer gel dosimeter based on acrylic monomers evaluated by MR Siemens Expert IT scanner was used in this study. Measured DVHs by gel dosimeter were compared with those obtained from the treatment-planning system. Additionally, several numerical parameters were implemented for comparison of DVHs: (1) mean dose absorbed in the reference volume, (2) total volume of 30, 50, and 80% isodose, (3) Pearson's correlation coefficient, and (4) euclidian distance. The outlined parameters showed a relatively high degree of agreement between the measured and calculated DVH data for all seven different stereotactic treatment plans using different irradiation techniques simulated in this study. The most serious practical limitation of the whole measurement is the time required for gel preparation, the storage, and the MR readout after the gel irradiation. Copyright (C) 2010 S. Karger AG, Basel