Johansson B, Wickman G, Holmström T
Radiation Physics Department, Umeå University, Sweden.
Phys Med Biol. 1995 Apr;40(4):575-87. doi: 10.1088/0031-9155/40/4/006.
Properties such as sensitivity, general recombination and reproducibility of liquid-filled parallel-plate ionization chambers for dosimetry in low-dose-rate brachytherapy radiation fields have been evaluated. Two different dielectric liquids, isooctane (C8H(1)8) and tetramethylsilane (Si(CH3)4), have been used as sensitive media in chambers having a coin-shaped sensitive volume of 3 mm in diameter and 1 mm thickness. An electric field strength of 300 kV m-1 was found to be optimal with respect to sensitivity, leakage current and general recombination. At absorbed dose rates from 0.1-100 mGy min-1 the ionization charge measurements at an irradiation time of 1 min showed a reproducibility better than 1%, and a general recombination not exceeding 0.5%. The calibration--absorbed dose to water against ionization charge at a 60Co reference source--did not show any significant change over an observation time of one year for any of the chambers.
已对用于低剂量率近距离放射治疗辐射场剂量测定的充液平行板电离室的灵敏度、一般复合和再现性等特性进行了评估。两种不同的介电液体，异辛烷（C8H(1)8）和四甲基硅烷（Si(CH3)4），已被用作敏感介质，用于直径为3毫米、厚度为1毫米的硬币形敏感体积的电离室中。发现300 kV m-1的电场强度在灵敏度、漏电流和一般复合方面是最佳的。在0.1 - 100 mGy min-1的吸收剂量率下，在1分钟的照射时间内进行的电离电荷测量显示再现性优于1%，且一般复合不超过0.5%。对于任何一个电离室，在一年的观察时间内，以60Co参考源的电离电荷对水的校准吸收剂量均未显示出任何显著变化。
