胶片测量不同间距^(125)I粒子照射的剂量学研究

Dosimetric research on ^(125)I seeds arranged in different spacing by using film dosimeter

目的探讨同活度、同数量^(125)I粒子不同间距轴向排列照射的相对剂量学效应。方法 27张胶片随机分为A、B、C组,每张胶片接受3枚1.48×10~7Bq^(125)I粒子照射,3组粒子呈线性排列,轴向间距分别为1、5、10 mm。图像分析软件计算测量胶片上粒子照射周围灰度值为20、25、30、40的等灰度曲线及曲线所含面积。结果多样本均数比较方差分析显示,A、B、C组间20、25灰度等灰度曲线下面积差异均有统计学意义(P<0.001);A、B组间30灰度等灰度曲线下面积差异无统计学意义(P>0.05),A、C组间和B、C组间30灰度等灰度曲线下面积差异均有统计学意义(P<0.001);A、B、C组间40灰度等灰度曲线下面积差异无统计学意义(P=0.99)。结论同活度、同数量^(125)I粒子不同间距排列,直接影响周边照射剂量分布。特定剂量范围内粒子间距1 mm排列,可能较5、10 mm排列具有更好的照射剂量分布。

Objective To investigate the dosimetric effect of same activity and same number of 125I seeds arranged in axial train but with different spacing. Methods A total of 27 film dosimeters were randomly and equally divided into group A, B and C. Each film was irradiated by three 125I seeds （activity of 1.48×10^7 Bq）. The seeds were arranged in line, and their axial spacing was 1 mm, 5 rain and 10 mm respectively. Image analysis software was used to draw iso-gray contour curves of 20, 25, 30 and 40 gray value on the films, and to calculate the areas contained by each curve. Results Multi- sample mean comparison variance analysis showed that the differences in area contained by 20 and 25 isogray contour curves were statistically significant between each other among the three groups （P〈0.001）. The difference in area contained by 30 iso-gray contour curve between group A and group B was not statistically significant （P〉 0.05）, while the difference in area contained by 30 iso-gray contour curve between group A and group C as well as between group B and group C was statistically significant （P〈0.001）. No statistically significant difference in area contained by 40 iso-gray contour curve existed between each other among the three groups （P=0.99）. Conclusion Different spacing arrangement of same activity and same number of 125I seeds can directly influence the peripheral dose distribution. In specific dose range, seed-spacing of 1 mm arrangement may obtain better dose distribution than seed- spacing of 5 mm or 10 mm arrangement can do.