摘要
目的：通过对头部体模扫描试验,探讨成人头颅CT低剂量扫描参数。方法：以层厚10 mm,扫描时间为1 s,通过改变mA值,以10 mA为间隔,20-300 mA间29个不同mA条件对头部体模进行轴向扫描,对容积CT剂量指数（CTDIvol）、噪声（SD）和对比-噪声比（CNR）进行客观评价分析与统计学处理,对图像低密度分辨力进行主观评价。结果：①CTDIvol随mAs增大而增大,呈线线关系;与300 mAs的CTDIvol（42 mGy）比较,80-150 mAs的CTDIvol（11-21 mGy）下降73%-50%。②SD值随mAs升高而降低;SD值随mAs变化曲线可分为SD改变非常显著段（20-50 mAs）、显著段（50-80 mAs）、缓坡段（90-150 mAs）和平缓段（160-300 mAs）。③CNR随mAs改变与SD值改变相反。④SD值与CNR统计学处理：20 mAs与30 mAs、30 mAs与50 mAs5、0 mAs与80 mAs、80 mAs与150 mAs、150 mAs与300 mAs的各SD值及CNR有统计学差异（P〈0.05）;160-300 mAs的各SD值与CNR无统计学差异（P〉0.05）。⑤图像LCR主观评价：20-50 mAs,分辨低密度圆柱体困难;50-80 mAs,主观图像质量明显下降,图像对诊断有影响;90-150 mAs主观图像质量有一定改变;160-300 mAs主观图像质量改变不明显。结论：80-150 mAs为低对比要求较高的成人颅脑低剂量平扫可用区间,为临床降低扫描剂量提供了依据。临床患者检查,可以用100 mAs进行平扫,CT剂量指数明显降低。
Objective：To develop optimized acquisition parameters for low-dose CT of the adult head.Methods：A head phantom was scanned with the following parameters：slice thickness,10mm;scanning time,1s,tube current,20-300mA at each 10mA interval.The CT dose volume index（CTDIvol）,the imaging noise（SD,standard deviation of CT number） and contrast-to noise-ratio（CNR） were measured and analyzed statistically.The low contrast resolution（LCR） was assessed subjectively.Results：①The CTDIvol was linearly increased according to the rise of tube current.The CTDIvol values were 42mGy at 300mAs,21mGy at 150mA,11mGy at 80mA.②The SD value was reduced by increasing tube current.The SD-mAs curve was extremely steep downward in segment 20-50mAs,steep downward in segment 50-80mAs,transitional in segment 90-150mAs,and flat in segment 160-300mAs.③CNR was increased according to the rise of mAs.④CNR was significantly（P0.05） increased with the descent of SD value of 20-30mAs,30-50mAs,50-80mAs,80-150mAs,and 150-300mAs,however,CNR was not significantly increased（P0.05） with the descent of SD value of w 160-300mA.⑤In terms of subjective assessment of LCR,it was difficult to differentiate the low density cylinders at 20-50mAs.Subjective image quality was obviously decreased and the diagnosis of head diseases could be significantly influenced between 50 and 80mAs.Subjective image quality was decreased to a certain degree between 90 and 150mAs,while degradation of subjective image quality wasn＇t found at 160-300mAs.Conclusion：80-150mAs is optimized acquisition parameter for low-dose unenhanced CT scan of the adult head,providing diagnostic quality with reasonable radiation dose for the patients in clinical practice.The CTDIvol can be remarkably reduced with 100mAs in clinical examination.
出处
《放射学实践》
北大核心
2011年第8期886-889,共4页
Radiologic Practice
基金
广西贺州市科学技术局科研课题项目(贺科能0911002Y)
