Servicio de Radiofísica Hospitalaria, Hospital Universitario "Virgen Macarena", Avda. Doctor Fedriani, 3, E-41009 Sevilla, Spain.
Phys Med. 2013 Nov;29(6):670-6. doi: 10.1016/j.ejmp.2012.07.003. Epub 2012 Jul 31.
To simulate the Bebig model I125.S16 source and obtain AAPM Task Group Report 43 brachytherapy dosimetry parameters for comparison to consensus and previously published values. The seed model will then be incorporated into a Monte Carlo model of COMS eye plaques and simulation results will be used for seed-carrier set modeling in a commercial planning system.
PENELOPE was used to simulate the seed and the applicators for different sizes and loading levels. The corresponding TG-43U1 dosimetric parameters of the seed were calculated. Bebig Plaque Simulator was used.
The air kerma strength, the dose rate constant and the radial dose and 2D anisotropy functions found showed a good agreement with those published by other authors. Dose distributions were determined for the 12 and 20 mm COMS plaques loaded with a single seed and for the 12 mm plaque fully loaded. The plaque effect on the eye dose and the interseed absorption were evaluated. If the plaque is loaded with a single seed, the dose in the central axis reduces about 10% at 5-6 mm depth with respect to the case in which the plaque is not present. This reduction does not depend on the plaque size. When the plaque is fully loaded, an additional reduction in the dose with respect to the dose in water is observed mainly due to the effect of the Silastic carrier. The mean dose reduction in the central axis of the 12 mm plaque due to the interseed absorption was 0.5%. A new physics file for the planning system was created with the results obtained from the simulations. Results obtained using this adapted model for the 12 mm plaque fully loaded agreed with the corresponding simulation. Dose rate at the prescription point differs 4.7% when the adapted model is used instead of the default model.
Simulation results for COMS plaques are consistent with those published for other seeds. The planning system studied appears as a good tool for dose calculation in ophthalmic brachytherapy treatments. The new physics model, built up from Monte Carlo results, has been commissioned by comparing calculations made with the planning system to those obtained from Monte Carlo simulations.
模拟 Bebig 模型 I125.S16 源，并获得 AAPM Task Group Report 43 近距离治疗剂量学参数，以便与共识和先前发表的值进行比较。然后，将种子模型纳入 COMS 眼贴的蒙特卡罗模型中，并将模拟结果用于商业规划系统中的种子载体集建模。
使用 PENELoPE 模拟不同尺寸和装载水平的种子和施源器。计算种子的相应 TG-43U1 剂量学参数。使用 Bebig 贴剂模拟器。
空气比释动能强度、剂量率常数以及径向剂量和二维各向异性函数与其他作者发表的值吻合良好。确定了加载单个种子的 12 和 20mm COMS 贴剂以及完全加载的 12mm 贴剂的剂量分布。评估了斑块对眼部剂量和种子间吸收的影响。如果斑块加载单个种子，与不存在斑块的情况相比，在 5-6mm 深度处中央轴上的剂量减少约 10%。这种减少与斑块的大小无关。当斑块完全加载时，与水中的剂量相比，观察到剂量的额外减少，这主要是由于 Silastic 载体的影响。由于种子间吸收，在中央轴上的 12mm 斑块的平均剂量减少了 0.5%。使用模拟结果创建了一个新的规划系统物理文件。使用完全加载的 12mm 斑块的适配模型获得的结果与相应的模拟结果一致。当使用适配模型而不是默认模型时，在规定点的剂量率差异为 4.7%。
COMS 贴剂的模拟结果与其他种子发表的结果一致。所研究的计划系统似乎是眼科近距离放射治疗剂量计算的良好工具。新的物理模型是从蒙特卡罗结果建立的，并通过将计划系统的计算与蒙特卡罗模拟的结果进行比较来验证。
