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目的:探讨平衡帽材料对准直器散射因子（Sc）测量值的影响。材料和方法:采用由A-150塑料和铜制做成的两种平衡帽。用Farmer2570剂量仪分别测量6MV X线不同射野条件下电离室的电离值,并归一到参考射野,得到两组Sc值进行比较。结果:使用铜材平衡帽时,电离室的电离值明显高于使用A-150塑料平衡帽时电离室的电离值,最大高出14％,但两组Sc值的差异并不显著,均在1％以内。结论:虽然高密度材料和空气严重不等效,但对Sc测量值的影响较小,因此选用高密材料的平衡帽测量Sc（尤其在小野条件下）也不失为一种较好的方法。
OBJECTIVE: To investigate the effect of balance cap material on the measurement of collimator scattering factor (Sc). Materials and methods: Two balance caps made of A-150 plastic and copper are used. The Farmer2570 dosimeters were used to measure the ionization values of the ionization chamber under different conditions of 6MV X-ray and returned to the reference field respectively. The Sc values of the two groups were compared. Results: When using a copper balance cap, the ionization value of the ionization chamber was significantly higher than that of the ionization chamber when the A-150 plastic balance cap was used, up to a maximum of 14%. However, the difference in Sc between the two groups was not significant Within 1%. Conclusion: Although high-density materials and air are seriously ineffective, they have less effect on Sc measurements. Therefore, it is a good idea to use a high-density material cap to measure Sc, especially in the Ino conditions.