肿瘤放疗楔形照射野深度和射野大小对楔形因子的影响

The effects of depth and field size on wedge factor in the wedge field of oncology radiation

关键词:  直线加速器  楔形板  楔形因子  相对楔形因子

Key words:  linear accelerator  wedge filter  wedge factors  relative wedge factors

摘要:

探讨楔形野深度和射野大小对楔形因子的影响。方法：利用电离室法分别测量15°、30°、45°和60°楔形板在1.5 cm、5.0 cm、10.0 cm和15.0 cm深度处的5 cm×5 cm、10 cm×10 cm、15 cm×15 cm和20 cm×20 cm 4种照射野的楔形因子。结果：深度对楔形因子的影响较为明显。深度增加时楔形因子增大，且楔形板角度增大时深度对楔形因子的影响增大。对10 cm×10 cm照射野，在深度由1.5 cm增加到15.0 cm时，15 °～60 °楔形因子分别增加了1.9 %、3.4 %、4.9 %和6.1 %；射野大小对楔形因子也有一定影响。在5.0 cm深度处，4种楔形野当射野由5 cm×5 cm增加到20 cm×20 cm时，楔形因子分别增大了0.6 %、1.6 %、1.1% 和0.8 %。结论：临床剂量计算时，深度对楔形因子的影响应予以修正，建议采用相对深度楔形因子；射野大小对楔形因子的影响较小，可以忽略。

Abstract:

The effects of depth and field size on wedge factors were studied. Methods: The measurement of wedge factors were performed for 15°，30°，45°and 60°wedge filters at the depths of 1.5 cm, 5.0 cm, 10.0 cm and 15.0 cm using the ionization chamber. The field sizes varied from 5 cm×5 cm up to 20 cm×20 cm. Results: wedge factors had an obvious dependence on the depth of measurement. Wedge factors increased with the depth of measurement. For 10 cm×10 cm field at the depth of 1.5 cm up to 15.0 cm, wedge factors of 15°～60°wedge filters separately increased 1.9%，3.4%，4.9%t 6.1%. As wedge angle increased, the effects of depth on wedge factor became obvious. Wedge factors had a definite dependence on field sizes. Wedge factors of 15°～60° wedge filters separately increased 0.6%, 1.6%, 1.1% and 0.8% at the depth of 5.0cm as field sizes varied from 5 cm×5 cm up to 20cm×20cm. Conclusion: In clinical dose calculation, it was significant to use relative depth wedge factors. It should be adjusted that effect of depth on wedge factors. The impact of field sizes on wedge factors can be ignored.