Med Phys. 2013 Aug;40(8):080701. doi: 10.1118/1.4812675.
A novel (169)Yb low dose rate permanent implant brachytherapy source, the GammaClip™, was developed by Source Production & Equipment Co. (New Orleans, LA) which is designed similar to a surgical staple while delivering therapeutic radiation. In this report, the brachytherapy source was characterized in terms of "Dose calculation for photon-emitting brachytherapy sources with average energy higher than 50 keV: Report of the AAPM and ESTRO" by Perez-Calatayud et al. [Med. Phys. 39, 2904-2929 (2012)] using the updated AAPM Task Group Report No. 43 formalism.
Monte Carlo calculations were performed using Monte Carlo N-Particle 5, version 1.6 in water and air, the in-air photon spectrum filtered to remove photon energies below 10 keV in accordance with TG-43U1 recommendations and previously reviewed (169)Yb energy cutoff levels [D. C. Medich, M. A. Tries, and J. M. Munro, "Monte Carlo characterization of an Ytterbium-169 high dose rate brachytherapy source with analysis of statistical uncertainty," Med. Phys. 33, 163-172 (2006)]. TG-43U1 dosimetric data, including SK, Ḋ(r,θ), Λ, gL(r), F(r, θ), φan(r), and φan were calculated along with their statistical uncertainties. Since the source is not axially symmetric, an additional set of calculations were performed to assess the resulting axial anisotropy.
The brachytherapy source's dose rate constant was calculated to be (1.22±0.03) cGy h(-1) U(-1). The uncertainty in the dose to water calculations, Ḋ(r,θ), was determined to be 2.5%, dominated by the uncertainties in the cross sections. The anisotropy constant, φan, was calculated to be 0.960±0.011 and was obtained by integrating the anisotropy factor between 1 and 10 cm using a weighting factor proportional to r(-2). The radial dose function was calculated at distances between 0.5 and 12 cm, with a maximum value of 1.20 at 5.15±0.03 cm. Radial dose values were fit to a fifth order polynomial and dual exponential regression. Since the source is not axially symmetric, angular Monte Carlo calculations were performed at 1 cm which determined that the maximum azimuthal anisotropy was less than 8%.
With a higher photon energy, shorter half-life and higher initial dose rate 169Yb is an interesting alternative to 125I for the treatment of nonsmall cell lung cancer.
一种新型（169）Yb 低剂量率永久植入近距离放射治疗源，即 GammaClip™，由 Source Production & Equipment Co.（路易斯安那州新奥尔良）开发，其设计类似于手术钉，同时提供治疗辐射。在本报告中，根据 Perez-Calatayud 等人的《用于平均能量高于 50keV 的光子发射近距离放射治疗源的剂量计算：AAPM 和 ESTRO 的报告》[Med. Phys. 39, 2904-2929（2012）]，使用更新的 AAPM 任务组报告第 43 号格式对近距离放射治疗源进行了特征描述。
使用蒙特卡罗 N-Particle 5 版本 1.6 在水和空气中进行蒙特卡罗计算，根据 TG-43U1 建议和先前审查的（169）Yb 能量截止水平[D.C. Medich、M.A. Tries 和 J.M. Munro，“带有统计不确定性分析的 ytterbium-169 高剂量率近距离放射治疗源的蒙特卡罗特征”，Med. Phys. 33, 163-172（2006）]，过滤掉空气中的光子能谱以去除低于 10keV 的光子能。计算了 TG-43U1 剂量学数据，包括 SK、Ḋ（r，θ）、Λ、gL（r）、F（r，θ）、φan（r）和 φan 及其统计不确定性。由于源不是轴对称的，因此进行了另一组计算来评估由此产生的轴向各向异性。
计算出近距离放射治疗源的剂量率常数为（1.22±0.03）cGy·h-1·U-1。Ḋ（r，θ）水计算的不确定度确定为 2.5%，主要由截面不确定度引起。各向异性常数 φan 计算为 0.960±0.011，并通过在 1 到 10cm 之间积分各向异性因子并用与 r-2 成正比的加权因子获得。在 0.5 到 12cm 之间的距离处计算了径向剂量函数，在 5.15±0.03cm 处达到最大值 1.20。径向剂量值拟合为五阶多项式和双指数回归。由于源不是轴对称的，因此在 1cm 处进行了角度蒙特卡罗计算，确定最大的方位各向异性小于 8%。
由于具有更高的光子能量、更短的半衰期和更高的初始剂量率，169Yb 是治疗非小细胞肺癌的 125I 的一种有趣替代物。
