医用诊断X射线低反向散射性屏蔽材料的研究

目的 研究不同屏蔽材料及其组合对X射线反向散射率的影响, 探索散射率最低的医用诊断X射线机房屏蔽材料。
方法 采用AT1123型X-γ线剂量检测仪和铅准直器, 在100 kV曝光条件和几何条件不变情况下, 测量屏蔽材料表面45°反向散射线剂量和该位置主射线束剂量, 计算出与主射线束呈45°方向的反向散射率。
结果 在相同照射条件下, 不同屏蔽材料对X射线的散射率均不同(P < 0.01), 钡基纤维板最高, 铅板最低。相同厚度的同一种屏蔽材料, 铅板和铅玻璃随着接受照射的管电压的增加, 散射率略为下降, 其他屏蔽材料的散射率均出现上升趋势(P < 0.01)。不同厚度的同一屏蔽材料, 其反向散射率差异均有统计学意义(P < 0.01), 钡基纤维板和硫酸钡水泥板反向散射率随着厚度增加略为上升, 其他材料反向散射率随着厚度增加呈下降趋势(P < 0.01)。由不同成分组合的屏蔽材料对X射线的散射率不同(P均 < 0.01), 散射率与表层、下层材料种类均有关。
结论 反向散射率与照射管电压、屏蔽材料的种类和厚度以及材料的组合方式有关。建设医用诊断X射线机房, 应综合考虑各种屏蔽材料的特点, 选择多种屏蔽材料进行组合施工, 以降低机房建设成本, 减少X射线对人体健康的危害。

Effect of various shielding materials on low backscattering of medical diagnostic X-ray

Objective To examine the effect of shielding materials (single or combined)on the backscattering of X-ray used for medical diagnosis, and to find the optimized shielding materials against backscattering of medical diagnostic X-ray. Methods AT1123 X-γ ray dose detector and lead collimator were used to measure 45° backscattering dose and the main beam dose on the surface of shielding materials under both 100 kV voltage exposure and same geometric condition. The 45° backscattering ratio of X-ray was calculated. Results The backscattering ratio of X-ray varied when different shielding materials were used under the same irradiation condition (P < 0.01); the highest scattering ratio for the barium-based fiberboard and the lowest for the lead plate. The backscattering ratio slightly decreased with the increase of tube voltage, when the lead plate and lead glass with fixed thickness were used; by contraries, the backscattering ratio increased when other shielding materials were used (P < 0.01). The backscattering ratio differed significantly when the same shielding materials with different thickness were used (P < 0.01); the backscattering ratio slightly increased with the increase of thickness for the barium-based fiberboard and barium sulfate cement board, but slightly decreased for other materials (P < 0.01). The backscattering ratio varied significantly when different combination of shielding materials were used(P < 0.01), and the backscattering ratio was related both to the surface and the undersurface materials. Conclusion The backscattering of X-ray is related to the operated voltage and the type, thickness and combination of used shielding materials. When constructing the rooms of medical diagnostic X-ray examination, the property of different shielding materials should be considered, and combinations of various shielding materials should be selected to decrease the cost of construction and the hazard of X-ray to the human health.