Dosimetric characteristics of a reusable 3D radiochromic dosimetry material

Purpose To investigate the dosimetric characteristics of PRESAGE(REU) dosimeters. Methods Commercially available PRESAGE REU dosimeters (size of 10 mm x 10 mm x 45 mm) were divided into two groups, with one of the groups placed at room temperature of 22 degrees C (RT group) and another group placed at low temperature of 10 E C (LT group). A total of 3 dosimeters (set of dosimeters) were irradiated at a time, with doses of 1 Gy, 2 Gy, 4 Gy, 8 Gy, 12 Gy, 16 Gy, and 20 Gy, at a nominal dose rate of 400 MU/min at temperature of 22 degrees C. The dosimeters were irradiated three additional times by delivering the same doses as those during the initial irradiations (4 irradiation cycles). Optical density (OD) was assessed using optical CT scanning. Results Considering both linearity and sensitivity of the OD curves, R-2 above 0.95 and sensitivity above 0.04 Delta OD/Gy were observed at the 1 st irradiation (reading time <= 6 h) and 2 nd irradiation (reading time = 0.5 h) for the RT group. For the LT group, those values were observed at the 1 st irradiation (reading time <= 2 h), and the 3 rd and 4 th irradiations (both reading times = 0.5 h). Considering the reproducibility of signals in response to the same dose, dosimeters in the RT group showed average deviations among dosimeters less than 5% (the 1 st and 2 nd irradiations at the reading time of 0.5 h), while for dosimeters in the LT group showed average deviations among dosimeters less than 6% (the 3 rd and 4 th irradiations at the reading time of 0.5 h). For the rest, the OD curves were not linear, sensitivities of the dosimeters were lower than 0.04.OD/Gy, and OD deviations at the same dose were larger than 6%. Conclusions At room temperature, PRESAGE(REU) dosimeters could be used for dose measurement only for up to two dose measurement sessions. At low temperatures, usage of PRESAGE(REU) dosimeters for dose measurement seems to be possible from the 3 rd irradiation. When reusing PRESAGE REU dosimeters, the OD curve should be re-defined for every measurement session because the shape of this curve depends on the irradiation history.