Nath R, Meigooni A S, Muench P, Melillo A
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Med Phys. 1993 Sep-Oct;20(5):1465-73. doi: 10.1118/1.597110.
Anisotropy of dose distributions around 103Pd, 125I, and 192Ir sources for interstitial brachytherapy was examined. Dose rates around 125I models 6702 and 6711 and 192Ir sources were measured using lithium fluoride thermoluminescence dosimeters (LiF TLDs) in a water-equivalent, solid phantom. From these measured data for 125I and 192Ir and the previously published measured data for 103Pd, isodose rate contours were determined using a bivariate interpolation and smooth surface fitting algorithm. The anisotropy functions, F(r,theta), as defined by the Interstitial Collaborative Working Group (ICWG) for each source, were determined. Also, 4 pi-averaged anisotropy factors, phi an(r), for use in point source approximation, have been calculated at radial distances varying from 1-10 cm for 103Pd, 125I, and 192Ir sources. The anisotropy factors had average values of 0.90, 0.93, 0.95, and 0.98 for 103Pd, 125I model 6711, 125I model 6702, and 192Ir, respectively. The anisotropy factors determined from dose measurements in phantom are observed to be closer to unity than from those determined previously from in-air measurements. This can be attributed to the smoothing of two-dimensional dose distributions due to the presence of more scattered photons in the phantom measurements compared to in-air measurements. Because in-phantom measurements simulate more closely the brachytherapy patient, data from these experiments are recommended for a more accurate determination of dose distributions around clinical brachytherapy implants. In this work, we present a complete set of source data for two-dimensional dosimetry following the ICWG formalism.
研究了用于组织间近距离治疗的¹⁰³Pd、¹²⁵I和¹⁹²Ir源周围剂量分布的各向异性。使用氟化锂热释光剂量计（LiF TLD）在水等效固体模体中测量¹²⁵I型号6702和6711以及¹⁹²Ir源周围的剂量率。根据这些¹²⁵I和¹⁹²Ir的测量数据以及先前发表的¹⁰³Pd测量数据，使用双变量插值和平滑表面拟合算法确定等剂量率轮廓。确定了组织间协作工作组（ICWG）为每个源定义的各向异性函数F(r,θ)。此外，还计算了¹⁰³Pd、¹²⁵I和¹⁹²Ir源在1至10 cm不同径向距离处用于点源近似的4π平均各向异性因子φan(r)。¹⁰³Pd、¹²⁵I型号6711、¹²⁵I型号6702和¹⁹²Ir的各向异性因子平均值分别为0.90、0.93、0.95和0.98。观察到从模体剂量测量确定的各向异性因子比先前从空气中测量确定的各向异性因子更接近1。这可归因于与空气中测量相比，模体测量中存在更多散射光子导致二维剂量分布的平滑。由于模体测量更接近模拟近距离治疗患者，因此建议使用这些实验数据更准确地确定临床近距离治疗植入物周围的剂量分布。在这项工作中，我们按照ICWG形式给出了一套完整的二维剂量学源数据。
