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目的 探讨电子束照射野挡块对中心轴剂量和输出因子的影响。方法 用瑞典Sca ditronix公司生产的RFA 30 0型三维水箱及P型硅半导体探头对瓦里安 2 10 0C和 2 30 0C/D直线加速器的多种能量电子束进行了中心轴百分深度剂量 (PDD)扫描 ,并测量了照射野输出因子。结果 测得的PDD数据表明 ,电子束深度剂量对照射野铅挡大小有某种程度的依赖性 ,一般倾向是当照射野减小时表面剂量增大 ,治疗深度减小 ,最大剂量深度 (R10 0 )向表面移。这些变化在高能时最为明显。输出因子的测量结果说明 ,对不同能量电子束在不同限光筒条件下 ,输出因子随照射野铅挡大小改变的情况不尽相同。结论 临床治疗时使用的限光筒大小要尽量与实际照射野面积接近 ,在使用铅挡构成很小的照射野 (如 <6cm× 6cm)时 ,应实际测量输出因子 ,以减少剂量误差
Objective To investigate the effects of beam irradiation on the central axis dose and output factor. Methods A series of RFA 30 0 three-dimensional water tanks and P-type silicon semiconductor probes manufactured by Sca Ditronix of Sweden were used to measure the central axis percent depth dose of Varian 2 10 0C and 2 30 0C / D linear accelerator PDD) scan, and measured the radiation field output factor. Results The measured PDD data showed that electron beam depth dose has a certain degree of dependence on the lead size of the exposure field. The general trend is that when the irradiation field decreases, the surface dose increases, the treatment depth decreases, the maximum dose depth (R10 0 ) To the surface. These changes are most pronounced at high energy. The measurement results of the output factor show that the output factors vary with the size of the lead block of the irradiation field for different energy beams under different light-limiting conditions. Conclusions The size of the light-limiting tube used in clinical treatment should be as close as possible to the actual irradiation field. When using the lead block to form a small irradiation field (eg, <6cm × 6cm), the output factor should be actually measured to reduce the dose error