基于 TG-43U1 的 Model 67-6520Cs-137 近距离放射治疗源剂量学特性描述。

TG-43 U1 based dosimetric characterization of model 67-6520 Cs-137 brachytherapy source.

机构信息

Department of Radiation Medicine, North Shore University Hospital, 300 Community Drive, Manhasset, New York 11030, USA.

出版信息

Med Phys. 2009 Oct;36(10):4711-9. doi: 10.1118/1.3224462.

DOI:10.1118/1.3224462

PMID:19928102

Abstract

PURPOSE

Brachytherapy treatment has been a cornerstone for management of various cancer sites, particularly for the treatment of gynecological malignancies. In low dose rate brachytherapy treatments, 137Cs sources have been used for several decades. A new 137Cs source design has been introduced (model 67-6520, source B3-561) by Isotope Products Laboratories (IPL) for clinical application. The goal of the present work is to implement the TG-43 U1 protocol in the characterization of the aforementioned 137Cs source.

METHODS

The dosimetric characteristics of the IPL 137Cs source are measured using LiF thermoluminescent dosimeters in a Solid Water phantom material and calculated using Monte Carlo simulations with the GEANT4 code in Solid Water and liquid water. The dose rate constant, radial dose function, and two-dimensional anisotropy function of this source model were obtained following the TG-43 U1 recommendations. In addition, the primary and scatter dose separation (PSS) formalism that could be used in convolution/superposition methods to calculate dose distributions around brachytherapy sources in heterogeneous media was studied.

RESULTS

The measured and calculated dose rate constants of the IPL 137Cs source in Solid Water were found to be 0.930 (+/-7.3%) and 0.928 (+/-2.6%) cGy h(-1) U(-1), respectively. The agreement between these two methods was within our experimental uncertainties. The Monte Carlo calculated value in liquid water of the dose rate constant was null set=0.948 (+/-2.6%) cGy h(-1) U(-1). Similarly, the agreement between measured and calculated radial dose functions and the anisotropy functions was found to be within +/-5%. In addition, the tabulated data that are required to characterize the source using the PSS formalism were derived.

CONCLUSIONS

In this article the complete dosimetry of the newly designed 137Cs IPL source following the AAPM TG-43 U1 dosimetric protocol and the PSS formalism is provided.

摘要

目的

近距离治疗一直是各种癌症治疗的基石，特别是妇科恶性肿瘤的治疗。在低剂量率近距离治疗中，几十年来一直使用 137Cs 源。同位素产品实验室（IPL）推出了一种新的 137Cs 源设计（型号 67-6520，源 B3-561），用于临床应用。本工作的目的是在上述 137Cs 源的特征描述中实施 AAPM TG-43 U1 协议。

方法

在 Solid Water 水模材料中使用 LiF 热释光剂量计测量 IPL 137Cs 源的剂量学特性，并使用 GEANT4 代码在 Solid Water 和液体水中进行蒙特卡罗模拟计算。根据 TG-43 U1 建议，获得了该源模型的剂量率常数、径向剂量函数和二维各向异性函数。此外，研究了可用于卷积/叠加方法计算异质介质中近距离治疗源周围剂量分布的初级和散射剂量分离（PSS）公式。

结果

在 Solid Water 中，测量和计算的 IPL 137Cs 源的剂量率常数分别为 0.930（+/-7.3%）和 0.928（+/-2.6%）cGy h(-1) U(-1)。这两种方法之间的一致性在我们的实验不确定度范围内。液体水中剂量率常数的蒙特卡罗计算值为 null set=0.948（+/-2.6%）cGy h(-1) U(-1)。同样，测量和计算的径向剂量函数和各向异性函数之间的一致性也在+/-5%以内。此外，还推导出了使用 PSS 公式来描述源所需的表格数据。