Park Jong Min, Park So-Yeon, Choi Chang Heon, Chun Minsoo, Han Ji Hye, Cho Jin Dong, Kim Jung-In
Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.
Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
PLoS One. 2017 Jul 13;12(7):e0180970. doi: 10.1371/journal.pone.0180970. eCollection 2017.
To investigate the dosimetric characteristics of PRESAGEREU dosimeters.
Commercially available PRESAGEREU dosimeters (size of 10 mm × 10 mm × 45 mm) were divided into two groups, with one of the groups placed at room temperature of 22°C (RT group) and another group placed at low temperature of 10°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°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.
Considering both linearity and sensitivity of the OD curves, R2 above 0.95 and sensitivity above 0.04 ΔOD/Gy were observed at the 1st irradiation (reading time ≤ 6 h) and 2nd irradiation (reading time = 0.5 h) for the RT group. For the LT group, those values were observed at the 1st irradiation (reading time ≤ 2 h), and the 3rd and 4th 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 1st and 2nd 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 3rd and 4th 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 ΔOD/Gy, and OD deviations at the same dose were larger than 6%.
At room temperature, PRESAGEREU dosimeters could be used for dose measurement only for up to two dose measurement sessions. At low temperatures, usage of PRESAGEREU dosimeters for dose measurement seems to be possible from the 3rd irradiation. When reusing PRESAGEREU dosimeters, the OD curve should be re-defined for every measurement session because the shape of this curve depends on the irradiation history.
研究 PRESAGEREU 剂量仪的剂量学特性。
将市售的 PRESAGEREU 剂量仪（尺寸为 10 mm×10 mm×45 mm）分为两组，一组置于 22°C 的室温下（RT 组），另一组置于 10°C 的低温下（LT 组）。每次共照射 3 个剂量仪（剂量仪组），剂量分别为 1 Gy、2 Gy、4 Gy、8 Gy、12 Gy、16 Gy 和 20 Gy，在 22°C 的温度下以 400 MU/min 的标称剂量率进行照射。剂量仪再额外照射 3 次，给予与初始照射相同的剂量（4 个照射周期）。使用光学 CT 扫描评估光密度（OD）。
考虑 OD 曲线的线性和灵敏度，RT 组在第 1 次照射（读取时间≤6 h）和第 2 次照射（读取时间 = 0.5 h）时观察到 R2 高于 0.95 且灵敏度高于 0.04 ΔOD/Gy。对于 LT 组，在第 1 次照射（读取时间≤2 h）以及第 3 次和第 4 次照射（读取时间均为 0.5 h）时观察到这些值。考虑到相同剂量下信号的可重复性，RT 组剂量仪之间的平均偏差小于 5%（读取时间为 0.5 h 时的第 1 次和第 2 次照射），而 LT 组剂量仪之间的平均偏差小于 6%（读取时间为 0.5 h 时的第 3 次和第 4 次照射）。其余情况下，OD 曲线不呈线性，剂量仪的灵敏度低于 0.04 ΔOD/Gy，相同剂量下的 OD 偏差大于 6%。
在室温下，PRESAGEREU 剂量仪仅可用于最多两个剂量测量疗程的剂量测量。在低温下，从第 3 次照射开始似乎可以使用 PRESAGEREU 剂量仪进行剂量测量。重复使用 PRESAGEREU 剂量仪时，每次测量疗程都应重新定义 OD 曲线，因为该曲线的形状取决于照射历史。
