Islamic Azad University.
J Appl Clin Med Phys. 2013 Sep 6;14(5):90-103. doi: 10.1120/jacmp.v14i5.4302.
A glass seed consisting of the β--emitting radionuclide 90Y incorporated with radionuclide 153Sm as SPECT marker is proposed for potential application in brachytherapy in order to reduce the undesirable dose to healthy adjacent organs. The aim of this work is to determine the dosimetric characteristics, as suggested in the AAPM TG-60/TG-149 reports, for this seed using Monte Carlo simulation. Monte Carlo codes MCNP5, EGSnrc, and FLUKA were used to calculate the absorbed dose distribution around the seed. Dosimetric parameters, such as reference absorbed dose rate, radial dose function, and one-dimensional (1D) and two-dimensional (2D) anisotropy functions, were obtained. The computational results from these three codes are in agreement within 5.4% difference on average. The absorbed dose rate at the reference point was estimated to be 5.01 cGy h-1 μCi-1 and self absorption of YAS glass seed amounted to 30.51%. The results showed that, with thermal neutron bombardment of 5 hours in a typical flux, sufficient activity for applications in brachytherapy may be achieved. With a 5 mCi initial activity, the total dose of a YAS glass seed was estimated to be 1.38 Gy at 1.0 cm from the seed center. Comparing with gamma emitting seeds, the 90Y seed could reduce undesirable doses to adjacent organs, because of the rapid dose falloff of beta ray. Because of the high R90 value of 5.5 mm, fewer number of 90Y seeds will be required for an interstitial brachytherapy treatment using permanent implant, in comparison with other beta-emitting seeds. The results would be helpful in the development of the radioactive implants using 90Y glass seeds for the brachytherapy treatment.
一种玻璃种子，由 β 发射放射性核素 90Y 与放射性核素 153Sm 结合作为 SPECT 标记物，被提议用于潜在的近距离放射治疗应用，以减少对健康相邻器官的不良剂量。本工作的目的是根据 AAPM TG-60/TG-149 报告中的建议，使用蒙特卡罗模拟确定该种子的剂量学特性。使用 MCNP5、EGSnrc 和 FLUKA 蒙特卡罗代码计算种子周围的吸收剂量分布。获得了剂量学参数，如参考吸收剂量率、径向剂量函数以及一维（1D）和二维（2D）各向异性函数。这三个代码的计算结果平均差异在 5.4%以内。在参考点处的吸收剂量率估计为 5.01 cGy h-1 μCi-1，YAS 玻璃种子的自吸收量达到 30.51%。结果表明，在典型通量下用热中子辐照 5 小时，可以获得足够用于近距离放射治疗应用的活性。初始活性为 5 mCi 时，距离种子中心 1.0 cm 处 YAS 玻璃种子的总剂量估计为 1.38 Gy。与发射伽马射线的种子相比，90Y 种子由于β射线的快速剂量衰减，可以减少相邻器官的不良剂量。由于 R90 值高（5.5 毫米），与其他发射β射线的种子相比，在使用永久性植入物进行间质近距离放射治疗时，所需的 90Y 种子数量更少。这些结果将有助于使用 90Y 玻璃种子开发放射性植入物进行近距离放射治疗。
