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目的探讨适形铅挡块遮挡照射野外边缘情况下对表面辐射剂量的影响。方法将金属氧化物半导体场效应管(MOSFET)剂量探测器探头沿垂直于野边缘的直线布置在照射野外边缘,用不同宽度的低熔点适形铅块去屏蔽照射野外边缘,比较遮挡不同宽度铅块后与不遮挡时边缘区的剂量变化。结果遮挡适形铅挡块后与没有遮挡铅块比较,照射野边缘表面0～2mm内剂量跌落15%~20%,差异有高度统计学意义(P<0.01);遮挡适形铅块后与不遮挡铅块比较,照射野外2～10mm区域,剂量变化不显著,差异无统计学意义(P>0.05)。结论用低熔点铅挡块遮挡照射野既可形成适形放疗效果而且可降底照射野外边缘辐射剂量,有利于保护照射野外正常组织。
Objective To investigate the influence of the conformal lead block on the surface radiation dose in the case of shielding the edge of the field. Methods The detector of metal oxide semiconductor field effect transistor (MOSFET) was placed along the straight line perpendicular to the edge of the field at the edge of the irradiation field. The low-melting point lead with different width was used to shield the edge of the field. Dose changes in the marginal zone after and without occlusion. Results After masking the conformal lead block, there was a significant difference (P <0.01) between the dose drop of 0 ~ 2 mm in the edge of the irradiation field and the unleaded lead block with a significant difference (P <0.01) There was no significant difference in dose between the 2 ~ 10mm area exposed without occlusion lead block (P> 0.05). Conclusion Blocking the irradiation field with the low melting point lead block can not only form the conformal radiotherapy effect, but also reduce the radiation dose at the edge of the field to protect the normal tissues irradiated.