Meli J A, Meigooni A S, Nath R
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06510.
Int J Radiat Oncol Biol Phys. 1988 Mar;14(3):587-94. doi: 10.1016/0360-3016(88)90280-5.
Dosimetric characteristics of polystyrene, solid water, and polymethylmethacrylate were examined and compared to water to determine the suitability of these solid materials for the dosimetry of 192Ir. Ionization charge measured in each of the four media as a function of depth and depth-dose curves calculated by Monte Carlo simulation show that the three solids are equivalent to each other and to water under full scattering conditions. Photon energy spectra generated from the Monte Carlo simulation show little variation for the different media. Mass energy absorption coefficients and exposure-to-dose conversion factors were calculated as a function of depth for these spectra. Measured tissue attenuation factors are in excellent agreement with Meisberger's "selected" values. The radial dose function, which describes the change in dose with distance in phantom exclusive of the inverse square law, was calculated from the tissue attenuation factor and found to be in significant disagreement with Dale's Monte Carlo values. The reason for this discrepancy is discussed.
研究并比较了聚苯乙烯、固体水和聚甲基丙烯酸甲酯的剂量学特性，并与水进行比较，以确定这些固体材料用于192Ir剂量测定的适用性。在四种介质中测量的电离电荷作为深度的函数，以及通过蒙特卡罗模拟计算的深度剂量曲线表明，在全散射条件下，这三种固体彼此等效且与水等效。蒙特卡罗模拟生成的光子能谱在不同介质之间变化很小。针对这些能谱，计算了质量能量吸收系数和照射量与剂量转换因子随深度的函数关系。测量的组织衰减因子与迈斯伯格的“选定”值非常吻合。从组织衰减因子计算出描述模体中剂量随距离变化（不包括平方反比定律）的径向剂量函数，发现其与戴尔的蒙特卡罗值存在显著差异。讨论了这种差异的原因。
