Applicability of pure propane gas for microdosimetric measurements at photon energies relevant in brachytherapy is studied using the Monte Carlo-based FLUKA code. Monoenergetic photons in the energy range of 20-1250 keV and brachytherapy sources such as 103Pd, 125I, 169Yb, 192Ir, 137Cs and 60Co are considered in the study. Using the calculated values of energy deposited in the sensitive region of LET-1/2 tissue-equivalent proportional counter filled with pure propane gas and tissue-equivalent propane gas, values of density scaling factor for the site sizes of 1 and 8 μm are obtained. The study shows that density of propane gas should be lowered by a factor of about 0.93 for 169Yb, 192Ir, 137Cs and 60Co sources for the site sizes of 1-8 μm. For 125I source, the density of propane gas requires a scaling of 0.93 for 1 μm site size, whereas for site sizes 2-8 μm, density need not be altered. 103Pd source does not require density scaling for site sizes 1-8 μm.

中文翻译：

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纯丙烷气体在近距离治疗能量微量测定中的适用性：一项 FLUKA 研究。

使用基于蒙特卡罗的 FLUKA 代码研究了纯丙烷气体在与近距离放射治疗相关的光子能量下进行微剂量测量的适用性。研究中考虑了能量范围为 20-1250 keV 的单能光子和近距离放射治疗源，如 103Pd、125I、169Yb、192Ir、137Cs 和 60Co。使用填充纯丙烷气体和组织等效丙烷气体的LET-1/2组织等效正比计数器敏感区域沉积能量的计算值，获得1和8 μm位点尺寸的密度比例因子值. 研究表明，对于 169Yb、192Ir、137Cs 和 60Co 源，对于 1-8 μm 的位点，丙烷气体的密度应降低约 0.93 倍。对于 125I 源，对于 1 μm 位点尺寸，丙烷气的密度需要缩放 0.93，而对于 2-8 μm 的位点，密度不需要改变。103Pd 源对于 1-8 μm 的站点尺寸不需要密度缩放。