16层CT胸部血管成像Z轴调制低剂量研究  

Low-dose 16-slice spiral CT thoracic angiography using Z.axis modulation

作　　者：李惠民[1] 于红[2] 肖湘生[2] 虞岐崴[1] 

机构地区：[1]上海交通大学医学院附属新华医院放射科,200092 [2]第二军医大学附属长征医院影像科

出　　处：《中华放射学杂志》2011年第8期762-765,共4页Chinese Journal of Radiology

摘　　要：目的探讨16层CT胸部增强血管成像中Z轴调制合理低剂量的可行性。方法连续60例患者依序分为3组，每组20例，采用16层CT机，以3．5—4．0ml／s流率注射非离子型对比剂80～90ml后20～25s全肺扫描。采用Z轴调制的自动曝光控制（AEC）方式进行低剂量控制，以噪声指数，即均匀结构CT值测量时的标准差（SD）为变量，分别设A组SD=12，B组SD=15，C组SD=18。其余参数固定。每例患者扫描后即刻记录该次增强扫描的每层mAs和层数，并求得平均每层的mAs。分别评价横断面图像的噪声、伪影和CTA图像诊断接受度。差异显著性采用ANOVA法或Kruskal—Wallis法进行分析。结果A组mAs值（46．4±15．6）mAs最大，SD值（21．6±7．7）最小；B组mAs值（37．0±13．5）mAs居中，SD值（24．0±5．4）也居中；C组mAs值（20．7±6．3）mAs最小，SD值（30．7±6．9）则最大（H=31．390，P=0．000）。中间层面mAs值（A、B、C组分别为40．9，31．3，17．1）最小（F=9．578，H=22．230，F=21．180，P=0．000），噪声（A、B、C组分别为16．3，20．0，25．4）也最小（H=28．982，H=20．824，H=24．396，P=0．000）。CTA诊断接受度全部为优。胸中部降主动脉CT值分别为A组（335±85）HU，B组（334±56）HU，C组（427±63）HU。结论16层CT胸部增强血管成像Z轴调制低剂量成像是可行的，在增强良好的前提下，可以使用很低的剂量（如20mAs）进行CTA成像。Objective To explore the feasibility of low dose in MSCT thoracic angiography using Z-axis modulation. Methods The consecutive 60 patients were averagely divided into 3 groups and underwent thoracic angiography with a Toshiba Aquilion 16 scanner. The whole chest acquisition was commenced in automatic exposure control with Z-axis modulation 20-25 seconds after the contrast material was administered at the rate of 3.5-4.0 ml/s. With the noise index （SD） as the variable, three study groups were classified as A （ SD = 12）, B （ SD = 15 ）, and C （ SD = 18 ）. The mAs value per slice and the number of slices were recorded. The noises and artifacts of the axial images and the acceptability of CT angiogram were evaluated. The difference among the groups was compared by using ANOVA or nonparametric Kruskal-Wallis test. The threshold of the P value was 0. 05. Results The mean mAs value （46.4 ±15.6） mAs in group A was the highest but the SD value （21.6 ±7.7） was the lowest. The mean mAs value （37.0 ±13.5） and the SD value （24.0 ±5.4） in group B were the mediate. The mean mAs value （20. 7 ±6. 3） mAs in group C was the lowest but the SD value （ 30.7 ±6. 9 ） was the highest （ H = 31. 390, P = 0. 000）. The middle slice images in all patients had the smallest mAs （40. 9,31.3,17. 1 for group A,B,C, respectively; F = 9. 578, H = 22. 230, F = 21. 180, P = 0. 000） and SD values （ 16. 3, 20. 0,25.4 for group A, B, C, respectively; H = 28. 982, H = 20. 824, H = 24. 396, P = 0. 000）. The acceptability of CT angiogram in all patients was excellent. The CT value of descending aorta in group A, B, and C was （335 ±85 ） HU, （334 ±56）HU, and （427 ±63 ）HU, respectively. Conclusion Low dose in MSCT thoracic angiography using Z-axis modulation is feasible. We can use low dose （20 mAs, etc. ） for CT angiography when the contrast is significant.

关 键 词：胸部 体层摄影术 X线计算机 辐射剂量 

分 类 号：R816.4[医药卫生—放射医学]