Evaluating the Characteristics of a Novel DEMBIG Gel Dosimeter Using Computed Tomography

Over the last two decades, radiotherapy techniques have become more sophisticated. Three-dimensional (3-D) dose verification is required to ensure accurate dose delivery to the planning target volume. Gel dosimeters have the potential to measure the 3-D dose distribution and thus can be applicable in radiotherapy. In this study, we developed a novel DEMBIG gel dosimeter based on the 2-(Dimethylamino) ethyl acrylate (DEMA) monomer and used computed tomography (CT) to evaluate its characteristics. The DEMBIG gel was composed of 7% gelatin, 5% monomer, and 4% crosslinker. The gel response to a dose from 1 to 25 Gy was examined. The energy dependence, dose rate dependence, and spatial resolution were evaluated as well. After 24 h post-irradiation, the DEMBIG gel reached steady state. The average sensitivity at the photon energy of 6 MV was 0.459 HU/Gy (R²=0.995). The variations in sensitivity between 6-, 10-, and 15-MV photons were lower than 3%, and the difference in sensitivity between the dose rate of 100 and 600 MU/min was 28%. For a beam profile of 3 × 6 cm² and 6 MV, the 80%-20% penumbra for 0/5, 0/15, and 5/15 Gy can be around 2.73, 6.24, and 2.34 mm, respectively. We conclude that the DEMBIG gel dosimeter has high linearity of R² = 0.995 and high sensitivity of 0.459 HU/Gy. With CT readout, it could be used in clinical radiotherapy to verify the accuracy of 3-D dose delivery.