Clinic of Radiotherapy and Radiation Oncology-University Clinic of Medical Radiation Physics, Pius-Hospital, Carl von Ossietzky University, Oldenburg, Germany.
Phys Med Biol. 2017 Nov 21;62(24):N561-N572. doi: 10.1088/1361-6560/aa9636.
In modern HDR or LDR brachytherapy with photon emitters, fast checks of the dose profiles generated in water or a water-equivalent phantom have to be available in the interest of patient safety. However, the commercially available brachytherapy photon sources cover a wide range of photon emission spectra, and the range of the in-phantom photon spectrum is further widened by Compton scattering, so that the achievement of water-mimicking properties of such phantoms involves high requirements on their atomic composition. In order to classify the degree of water equivalence of the numerous commercially available solid water-mimicking phantom materials and the energy ranges of their applicability, the radial profiles of the absorbed dose to water, D , have been calculated using Monte Carlo simulations in these materials and in water phantoms of the same dimensions. This study includes the HDR therapy sources Nucletron Flexisource Co-60 HDR (Co), Eckert und Ziegler BEBIG GmbH CSM-11 (Cs), Implant Sciences Corporation HDR Yb-169 Source 4140 (Yb) as well as the LDR therapy sources IsoRay Inc. Proxcelan CS-1 (Cs), IsoAid Advantage I-125 IAI-125A (I), and IsoAid Advantage Pd-103 IAPd-103A (Pd). Thereby our previous comparison between phantom materials and water surrounding a Varian GammaMed Plus HDR therapy Ir source (Schoenfeld et al 2015) has been complemented. Simulations were performed in cylindrical phantoms consisting of either water or the materials RW1, RW3, Solid Water, HE Solid Water, Virtual Water, Plastic Water DT, Plastic Water LR, Original Plastic Water (2015), Plastic Water (1995), Blue Water, polyethylene, polystyrene and PMMA. While for Ir, Cs and Co most phantom materials can be regarded as water equivalent, for Yb the materials Plastic Water LR, Plastic Water DT and RW1 appear as water equivalent. For the low-energy sources Pd, Cs and I, only Plastic Water LR can be classified as water equivalent.
在现代 HDR 或 LDR 光子发射近距离放射治疗中，为了患者安全，必须能够快速检查在水中或水等效体模中生成的剂量分布。然而，商业上可获得的近距离放射治疗光子源涵盖了广泛的光子发射光谱，并且 Compton 散射进一步拓宽了体模内的光子光谱范围，因此，实现此类体模的水模拟特性涉及对其原子组成的高要求。为了对众多市售的固体水模拟体模材料的水等效程度及其适用的能量范围进行分类，使用蒙特卡罗模拟在这些材料中和相同尺寸的水体模中计算了水吸收剂量 D 的径向分布。这项研究包括 Nucletron Flexisource Co-60 HDR（Co）、Eckert und Ziegler BEBIG GmbH CSM-11（Cs）、Implant Sciences Corporation HDR Yb-169 Source 4140（Yb）的 HDR 治疗源以及 IsoRay Inc. Proxcelan CS-1（Cs）、IsoAid Advantage I-125 IAI-125A（I）和 IsoAid Advantage Pd-103 IAPd-103A（Pd）的 LDR 治疗源。由此，我们对周围的 Varian GammaMed Plus HDR 治疗 Ir 源的体模材料与水的比较（Schoenfeld 等人，2015 年）进行了补充。模拟在圆柱形体模中进行，体模由水或 RW1、RW3、固体水、HE 固体水、虚拟水、塑料水 DT、塑料水 LR、原始塑料水（2015 年）、塑料水（1995 年）、蓝水、聚乙烯、聚苯乙烯和 PMMA 组成。对于 Ir、Cs 和 Co，大多数体模材料都可以视为水等效的，而对于 Yb，塑料水 LR、塑料水 DT 和 RW1 似乎是水等效的。对于低能源 Pd、Cs 和 I，只有塑料水 LR 可被归类为水等效。
