Purpose. In this study, Monte Carlo (MC) simulations were done to relate the dose-response of the film to that in water. The effect of backscattering materials (PMMA, lead, polystyrene, and air) was investigated on its influence on film density for radionuclides including Am-241, Tc-99m, I-131, Cs-137. Methods. A BEAMnrc MC simulation was designed to score a phase-space file (PSF) below the container of the radionuclide under consideration to use as an input file for the subsequent DOSXYZnrc MC simulation. The geometry of the container holding the radionuclide was built using the component modules available in BEAMnrc. BEAMDP was used to investigate the container effect on the radionuclide spectrum as well as the fluence. The DOSXYZnrc simulation produced the absorbed dose in XR-QA2 and RT-QA2 Gafchromic^TM films. The DOSXYZnrc simulations were repeated for the Gafchromic^TM film now replaced with water to get the absorbed dose in water. From these results, conversion factors for the dose in water to the film dose for the different radionuclides, Am-241, Tc-99m, I-131, and Cs-137 were obtained. The actual film dose was calculated using the specific gamma exposure constant (Γ) at a distance of 50 cm for a point source approximation. From the BEAMnrc simulations, the particle fluence was extracted from PSFs to correct for the fluence at 0.1 cm below the sources from the fluence 50 cm away since the inverse square law will not apply to finite-size sources. The absorbed dose profiles in the film were compared to the absorbed dose profiles from the MC simulations. Results. A fitting function based on the neutron depletion model fits the optical density versus absorbed film dose data well and can be used as a calibration tool to obtain the film dose from its optical density. Lead as a backscatter material results in a higher optical density change but a lower absorbed dose. The XR-QA2 Gafchromic^TM film is more sensitive than the RT-QA2 Gafchromic^TM film, showing a more responsive optical density (OD) change in the energy range of radionuclides used in this study. Conversion factors were determined to convert the dose in water to the dose in Gafchromic^TM film. The Am-241 and I-131 simulated absorbed dose in the film to dose in water does not fluctuate as much as the simulated absorbed dose in film and water when using Tc-99m and Cs-137. Validation was shown for the comparison of the film and MC simulation absorbed dose profiles. Conclusions. MC BEAMnrc simulations are useful to simulate radionuclides and their containers. BEAMDP extracted energy spectra showed that the radionuclide containers produced a Compton effect on the energy spectra and added filtration on the lower spectral photon components. Extracted fluence ratios from PSFs were used to calculate the absorbed dose value at 0.1 cm distance from the source. By using the fit function, the dose in the film can be determined for known optical density values. The effect of the backscatter materials showed that the XR-QA2 Gafchromic^TM film results in higher optical density values than the RT-QA2 Gafchromic^TM film. The absorbed dose in both the films is comparable but not for a radionuclide such as Am-241 with an activity of 74MBq. The lead backscatter material showed to be the most prominent in optical density enhancement, and the air equivalent material was the least prominent. The XR-QA2 Gafchromic^TM film is the most sensitive and will be the best option if working with low energies. The absorbed dose in the XR-QA2 Gafchromic^TM film also showed a good comparison to the absorbed dose in water for the Am-241 radionuclide with an activity of 74MBq. The absorbed dose in the films compares well to the MC simulated doses.

目的。在这项研究中，进行了蒙特卡罗 (MC) 模拟，以将薄膜的剂量反应与水中的剂量反应联系起来。研究了后向散射材料（PMMA、铅、聚苯乙烯和空气）对包括 Am-241、Tc-99m、I-131、Cs-137 在内的放射性核素薄膜密度的影响。方法. BEAMnrc MC 模拟旨在对放射性核素容器下方的相空间文件 (PSF) 进行评分，以用作后续 DOSXYZnrc MC 模拟的输入文件。装有放射性核素的容器的几何形状是使用 BEAMnrc 中可用的组件模块构建的。BEAMDP 用于研究容器对放射性核素光谱和注量的影响。DOSXYZnrc 模拟在 XR-QA2 和 RT-QA2 Gafchromic ^TM薄膜中产生了吸收剂量。^{对 Gafchromic TM}重复了 DOSXYZnrc 模拟现在用水代替薄膜以获得水中的吸收剂量。根据这些结果，获得了不同放射性核素 Am-241、Tc-99m、I-131 和 Cs-137 在水中剂量到薄膜剂量的转换因子。实际胶片剂量是使用 50 cm 距离处的特定伽马曝光常数 (Γ) 计算的，用于点源近似。从 BEAMnrc 模拟中，粒子注量是从 PSF 中提取的，以校正距离 50 厘米远的注量低于源 0.1 厘米处的注量，因为平方反比定律不适用于有限尺寸的源。将薄膜中的吸收剂量分布与 MC 模拟的吸收剂量分布进行比较。结果. 基于中子耗尽模型的拟合函数很好地拟合了光密度与吸收的膜剂量数据，并且可以用作校准工具，以根据其光密度获得膜剂量。铅作为后向散射材料导致更高的光密度变化，但吸收剂量更低。XR-QA2 Gafchromic ^TM薄膜比 RT-QA2 Gafchromic ^TM薄膜更敏感，在本研究中使用的放射性核素的能量范围内显示出更灵敏的光密度 (OD) 变化。确定转换因子以将水中的剂量转换为 Gafchromic ^{TM中的剂量}电影。当使用 Tc-99m 和 Cs-137 时，Am-241 和 I-131 在薄膜中的模拟吸收剂量与在水中的剂量之间的波动不会像薄膜和水中的模拟吸收剂量那样波动。验证了薄膜和 MC 模拟吸收剂量曲线的比较。结论. MC BEAMnrc 模拟可用于模拟放射性核素及其容器。BEAMDP 提取的能谱表明，放射性核素容器对能谱产生了康普顿效应，并增加了对较低光谱光子成分的过滤。从 PSF 中提取的注量比用于计算距离源 0.1 cm 处的吸收剂量值。通过使用拟合函数，可以针对已知的光密度值确定薄膜中的剂量。背散射材料的影响表明，XR-QA2 Gafchromic TM 薄膜比 RT-QA2 Gafchromic ^TM薄膜产生更高的光密度值电影。两种薄膜的吸收剂量相当，但放射性核素如 Am-241 的活性为 74MBq 则不然。铅后向散射材料在光密度增强方面表现最突出，空气等效材料最不突出。XR-QA2 Gafchromic ^TM薄膜是最敏感的，如果使用低能量工作，它将是最佳选择。XR-QA2 Gafchromic ^TM薄膜中的吸收剂量也显示出与活性为 74MBq 的 Am-241 放射性核素在水中的吸收剂量的良好比较。薄膜中的吸收剂量与 MC 模拟剂量相当。