Soares C G
National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
Med Phys. 1991 Jul-Aug;18(4):787-93. doi: 10.1118/1.596632.
A revised approach to the problem of measuring a surface-absorbed dose from beta-particle-emitting ophthalmic applicators is presented. The technique chosen employs an extrapolation chamber equipped with a 4-mm-diam collecting electrode to make current measurements at air gaps from 0.08 to 0.20 mm at 0.02-mm intervals. These data yield a linear relationship between current and air gap, the slope of which is used to determine average surface-absorbed-dose rate over the central area of the source. For additional information about the distribution of the activity over the source surface, autoradiographs using calibrated radiochromic dye films are analyzed to map the dose-rate profile across the surface of the applicator. Experiments varying several parameters of the extrapolation chamber measurement, including collecting electrode area, voltage gradient, range of air gaps used, and entrance foil material, are described. Also treated are calibrations of, and a description of the use of, radiochromic dye films for source profiling. Experiments for determining correction factors for the extrapolation chamber measurements are described, and an assessment of the uncertainties associated with these measurements is given.
本文提出了一种测量β粒子发射眼科敷贴器表面吸收剂量问题的改进方法。所选用的技术采用了一个配备4毫米直径收集电极的外推电离室，以便在气隙为0.08至0.20毫米、间隔为0.02毫米的情况下进行电流测量。这些数据得出了电流与气隙之间的线性关系，其斜率用于确定源中心区域的平均表面吸收剂量率。为了获取有关源表面活度分布的更多信息，对使用校准过的放射变色染料膜的放射自显影片进行分析，以绘制敷贴器表面的剂量率分布图。文中描述了改变外推电离室测量的几个参数的实验，包括收集电极面积、电压梯度、所用的气隙范围以及入射箔材料。还论述了放射变色染料膜用于源分析的校准方法及使用说明。描述了确定外推电离室测量校正因子的实验，并给出了与这些测量相关的不确定度评估。
