多层螺旋CT低剂量扫描在小儿胸部的应用探讨

目的:评价小儿胸部多层螺旋CT低剂量与常规剂量扫描的图像质量,探讨低剂量扫描在小儿胸部应用的可行性。材料与方法:(1)随机选择肺部感染的患儿30例,先常规剂量(150mAs)扫描,再在感染灶局部加作低剂量扫描,剂量为50,35及15mAs。其他参数为:120kV,床进28.8mm/圈,0.5s/圈,16×1.5mm准直,重建层厚及间隔均为3mm。分别记录不同剂量扫描时的CT权重剂量指数(CTDIw)及剂量长度乘积(DLP)。(2)由2位高年资医师按优、良、合格及不合格的等级盲法评价不同剂量的图像质量,结果进行统计学处理。结果:(1)小儿胸部35mAs和15mAs的CTDIw与常规剂量150mAs的比值分别为23.0%及10.0%,其DLP与常规剂量比值为23.3%和10.0%。(2)图像质量评价结果:150,50,35,15mAs的可诊断图像χ2检验,肺窗P>0.05,纵膈窗P<0.05,提示上述剂量肺窗图像差异无显著性意义,纵膈窗图像差异有显著性意义。用150,50,35mAs的可诊断图像进行χ2检验,P>0.05,提示其差异亦无显著性意义。结论:多层螺旋CT低剂量扫描适用于小儿胸部检查,在保证图像质量的前提下,采用35mAs左右的扫描条件较为适宜。

The Application of low-dose Multislice Spiral CT in Pediatric Chest

Objective:To evaluate the pediatric chest images aquisited by multislice spiral CT(MSCT) with low-dose and conventional parameters,and to explore the possibility of low-dose scan in the examination of pediatric chest.Material and Methods:(1)30 children with infection in the lungs were selected randomly. First,they underwent conventional chest scan(the tube current was 150mAs),then 50,35,15mAs were applied in the low-dose scans of the same focus after they were detected. The other technical parameters were:120Kv,28.8mm feed/rotation,0.5s/rotation,16*1.5mm collimation,and 3mm slice thickness.Weighted CT dose index(CTDIw) and Dose lenth product(DLP) with diffetent scan protocols were compared.(2)2 radiologists blinded to the tube current accsssed the images in random order by using 4 grades:good,adequate,diagnostic and poor,then the results were analyzed statistically.Results:(1) The CTDIw of 35mAs and 15mAs were only 23.0% and 10.0% of 150mAs's,and so were DLP.(2)Results of image quality evaluation:The percentage of the diagnostic images with lung window had no significant difference between 150,50,35 and 15mAs(P>0.05),and there was no significant difference between 115,50 and 35mAs images with mediastinum window either. Conclusion:the convertional dose scan can be replaced by low-dose scan in pediatric chest examination.It's suitable to choose tube current 35mAs in the examination of pediatric chest by MSCT for image quality assurance.