Sharma S D, Bianchi C, Conte L, Novario R, Bhatt B C
Cattedra di Fisica Medica, Dipartimento di Scienze Cliniche e Biologiche, Universita degli Studi dell' Insubria, 21100 Varese, Italy.
Phys Med Biol. 2004 Sep 7;49(17):4065-72. doi: 10.1088/0031-9155/49/17/016.
The dose distribution produced by the high-dose-rate (HDR) 192Ir source is inherently anisotropic due to self-absorption by the high-density source core, oblique filtration by the source capsule and the asymmetric geometry of the source capsule. To account for the dose distribution anisotropy of brachytherapy sources, AAPM Task Group No 43 has included a two-dimensional anisotropy function, F(r, theta), in the recommended dose calculation formalism. Gafchromic HS radiochromic film (RCF) was used to measure anisotropy function for microSelectron HDR 192Ir source (classic/old design). Measurements were carried out in a water phantom using specially fabricated PMMA cylinders at radial distances 1, 2, 3, 4 and 5 cm. The data so generated are comparable to both experimental and Monte Carlo calculated values for this source reported earlier by other authors. The RCF method described in this paper is comparatively high resolution, simple to use and is a general method, which can be applied for other brachytherapy sources as well.
由于高密度源芯的自吸收、源包壳的斜向过滤以及源包壳的不对称几何形状，高剂量率（HDR）192Ir 源产生的剂量分布本质上是各向异性的。为了考虑近距离放射治疗源的剂量分布各向异性，美国医学物理学家协会第43任务组在推荐的剂量计算形式中纳入了二维各向异性函数F(r,θ)。使用Gafchromic HS放射变色薄膜（RCF）来测量microSelectron HDR 192Ir源（经典/旧设计）的各向异性函数。测量在水模体中进行，使用专门制作的聚甲基丙烯酸甲酯（PMMA）圆柱体，径向距离分别为1、2、3、4和5厘米。如此生成的数据与其他作者先前报道的该源的实验值和蒙特卡罗计算值均具有可比性。本文所述的RCF方法具有相对较高的分辨率，使用简单，是一种通用方法，也可应用于其他近距离放射治疗源。
