多排螺旋CT几何效率影响因素初步研究

Research on influencing factors of geometric efficiency on MDCT

目的：研究多排螺旋CT几何效率与准直宽度及管电压的关系。方法：使用长杆电离室测量不同准值宽度以及管电压下体模内剂量分布曲线并计算其几何效率。结果：多排螺旋CT的几何效率为11%～68%，其中中心位置的几何效率为11%～49%，边缘4个位置的几何效率为16%～68%，加权几何效率为17%～58%。随准直宽度的增加，几何效率明显增高，而管电压对几何效率的影响不明显。结论：多排螺旋CT几何效率受准直宽度影响较大，因此在实际临床操作中应选择适当的准直宽度进行扫描以减小患者的辐射剂量负担。

Objective：To investigate the dependence of geometric efficiency （GE） on beam collimation and tube voltage.Methods： The dose profile was measured under the conditions of different collimations and tube voltages and GE was calculated.Results： GE was found to be from 11% to 68%, GE at central position and periphery were found to range from 11% to 49% and 16% to 68% respectively, and weighted GE was found to be from 17% to 58%. GE was increased with beam collimation, while it was less pronounced on tube voltages.Conclusion：The dependence of GE on collimation was significant. Therefore, operators should choose appropriate collimations to reduce the dose burden of patients in CT examinations.