Sánchez-Reyes A, Tello J I, Guix B, Salvat F
Servicio de Oncología Radioterápica, Hospital Clínic Universitari de Barcelona, Spain.
Radiother Oncol. 1998 Nov;49(2):191-6. doi: 10.1016/s0167-8140(98)00095-4.
Beta emitting 106Ru applicators are widely used to treat choroidal melanoma. In view of the importance of clinical applications of this radioisotope and the relative lack of knowledge of the dose distributions, three-dimensional dose maps of two concave applicators were calculated by means of Monte Carlo simulation.
Simulations of small CCA and CCB concave applicators manufactured by Bebig were performed using the Monte Carlo code PENELOPE, which allows the description of the structure (geometry and materials) of the applicator in detail. Electrons are emitted from the 106Ru nuclei isotropically, with initial energy randomly sampled from the corresponding Fermi spectra and with initial positions uniformly distributed on the radioactive layer. Primary electrons, as well as the produced delta-rays, are assumed to be absorbed in the medium when they slow down to an energy of 70 keV. Bremsstrahlung photons with energies larger than 7 keV are also simulated. The simulation code has been run on a 166 MHz PENTIUM PC.
Three-dimensional dose distributions produced by the CCA and CCB applicators in a water sphere, concentric with the applicator, were evaluated. To minimize the magnitude of statistical uncertainties, advantage has been taken of the cylindrical symmetry of the problem. The relative depth-dose (along the symmetry axis of the applicator) was also evaluated from the applicator surface up to distances larger than I cm, with statistical uncertainties of a few percent. Results compare well with data supplied by the manufacturer.
We have performed accurate Monte Carlo calculations of three-dimensional dose distributions from CCA and CCB 106Ru applicators. The results, presented in the form of two-dimensional maps, depth-dose distributions along the symmetry axis and lateral dose profiles, provide a detailed description of the dose delivered in treatments of choroidal melanoma.
发射β射线的106钌敷贴器被广泛用于治疗脉络膜黑色素瘤。鉴于这种放射性同位素在临床应用中的重要性以及对剂量分布的了解相对较少，通过蒙特卡罗模拟计算了两种凹面敷贴器的三维剂量图。
使用蒙特卡罗代码PENELOPE对Bebig生产的小型CCA和CCB凹面敷贴器进行模拟，该代码允许详细描述敷贴器的结构（几何形状和材料）。电子从106钌原子核各向同性发射，初始能量从相应的费米光谱中随机采样，初始位置在放射性层上均匀分布。初级电子以及产生的δ射线在减速到70 keV能量时被假定吸收在介质中。能量大于7 keV的轫致辐射光子也进行了模拟。模拟代码在一台166 MHz奔腾个人计算机上运行。
评估了CCA和CCB敷贴器在与敷贴器同心的水球中产生的三维剂量分布。为了使统计不确定性的幅度最小化，利用了问题的圆柱对称性。还从敷贴器表面到大于1 cm的距离评估了相对深度剂量（沿敷贴器对称轴），统计不确定性为百分之几。结果与制造商提供的数据比较良好。
我们对CCA和CCB 106钌敷贴器的三维剂量分布进行了精确的蒙特卡罗计算。以二维图、沿对称轴的深度剂量分布和横向剂量剖面形式呈现的结果，详细描述了脉络膜黑色素瘤治疗中所给予的剂量。
