不同管电流技术对胸部CT健康体检图像质量的影响及辐射剂量的优化

Study on image quality of chest CT physical examination with different tube current techniques,and radiation dose optimization

目的探讨胸部CT健康体检达到诊断要求且辐射剂量最低的管电流。方法将50例健康体检者随机分5组,每组10例:试验组设立管电流梯度分别为20 mA、30 mA、50 mA,自动mA的四个组;对照组为220mA。分别对上述5组的纵隔窗及肺窗进行质量评定。对试验组及对照组进行t检验,试验组间采用方差分析。找出符合诊断要求及辐射剂量最低的管电流。结果试验组4个管电流梯度的容积剂量指数(Ctdivol)剂量长度值(Dlp),有效吸收剂量(ED)均低于对照组。经统计学分析,二者差异均有统计学意义(P<0.05)。试验组中以20 mA组的Ctdivol、Dlp、ED最低。试验组4个剂量梯度(20 mA、30 mA、50 mA、自动mA组)的纵隔窗及肺窗的质量评分分别为:1.99±0.31/2.88±0.62,2.49±0.52/3.21±0.54,3.55±0.65/4.04±0.63,4.97±0.12/4.97±0.12。当纵隔窗及肺窗大于3时定义为可以达到诊断要求,因此管电流30 mA时被认为是可以作为胸部低剂量CT体检的最佳管电流。结论管电流30 mA时可以作为胸部低剂量CT体检的最低剂量值。

Objective To investigate the lowest dose of the tube current on the chest CT physical examination which can satisfy the diagnostic requirements.Methods The 50 persons subjected to physical examination were randomly divided into 5 groups,with an average of 10 persons:the 4 trial groups were set up 4 dose gradient,they were 20mA,30mA and 50mA,and automatic mA respectively.Control group was set as 220mA.The quality of the mediastinum window and lung window in above 5 groups were evaluated respectively.The t test was performed in trial groups and control group,and the analysis of variance was used among trial groups.Then the lowest radiation dose were seeked which dose can meets the diagnostic requirements.Results The volume dose index(Ctdivol),dose length product(Dlp)and effective absorbed dose(ED)of the 4 dose gradients in trial groups were lower than those in control group.The both's differences were statistically significant(P<0.05).The Ctdivol,Dlp and ED in the 20mA group were the lowest in trial group.Trial group received 4 doses(20mA,30mA,50mA gradient,automatic mA group)quality score of the mediastinal window and pulmonary window respectively:1.99±0.31/2.88±0.62,2.49±0.52/3.21±0.54,3.55±0.65/4.04±0.63,4.97±0.12/4.97±0.12.When the mediastinum window and the lung window were larger than 3,defined as the diagnostic requirements,the 30mA group was considered to be the best tube current for chest low dose CT examination.Conclusion When the tube current is 30MA,it can be used as the lowest dose for chest low dose CT examination.