多层螺旋CT膝关节低剂量扫描对影像质量的影响

目的:探讨多层螺旋CT低剂量膝关节扫描的可行性及其对图像质量的影响。方法:收集2009年5月~10月,100例行膝关节CT扫描者根据扫描的管电压高低分为2组(其他扫描条件不变),每组50例,A组110kV和B组80kV(管电压选择110kV和80kV是依据分别观察10例在此条件下扫描的患者图像,应用80kV而不影响诊断)。测量膝关节髌骨上缘水平后方肌肉软组织固定ROI的CT值,以CT值的标准差(SD)作为图像噪声。通过CT机自动得到平均容积CT剂量指数(CTDIvol),再计算出剂量长度乘积(DLP)。获得的图像通过双盲法进行质量评分,对两组CTDIvol值、DLP值、图像噪声、及图像质量评分均值用t检验进行比较。结果:A组和B组的CTDIvol值分别为(5.29±0.23)和(2.08±0.15)mGy,DLP值分别为(61.26±11.64)和(24.21±4.64)mGy.cm,B组较A组下降约(60.68)%,两者之间差异均有统计学意义(t值分别为(82.4)和(20.91),P0.01,B组噪声均值略高于A组(分别为12.22±2.97和16.55±2.96),t=-7.299,P=0.000,但两组图像质量平均评分分别为(4.86±0.40)分和(4.82±0.44)分,差异无统计学意义(t=0.475,P0.05)。结论:16层螺旋CT应用低kV设置(80kV)扫描膝关节可大幅度降低辐射剂量且所得图像质量不影响诊断。

The influence of multi-slice spiral CT low-dose scan on image quality

Objective：To explore the feasibility of multi-slice spiral CT low-dose scan in knee joint and it＇s influence on image quality.Methods：According to the tube voltage of the scan,divide 100 cases receiving knee-joint CT scan during may,2009 to oct,2009 into two groups,each group contain 50 cases,the tube voltage of A group and B group were 110 kV and 80 kV.Measure the CT values of the fixed ROI that the muscles and soft tissue behind the upper edge of patella,use standard deviation（SD） of CT values as the image noise.Mean volume CT dose index（CTDIvol） that zutomatically got through CT,then calculate the dose-length product（DLP）.Use double-blind method to evaluate CT image.Use t test to compare two group＇s CTDIvol values,DLP values,image noise and image quality score.Results：The CTDIvol values of A group and B group were（5.29±0.23） and（2.08±0.15） mGy,DLP values were（61.26±11.64） and（24.21±4.64） mGy.cm,group Bdcreased by about 60.68% than group A,the differences between the two were statistically significant t values were 82.4 and 20.91,pvalues are 0.01,the mean noise value of B group was slightly higher than A group（12.22±2.97 and 16.55±2.96）,t=-7.299,P=0.000,but the mean image quality score（（4.86±0.40） points and（4.82±0.44） points）,have no statistically significant difference（t=0.475,P0.05）.Conclusion：When multi-slice low-dose CT technology 80 kV was correctly applied that may availably protect the patients and guarantee image quality.