【摘要】 目的 探讨管电流、管电压对图像CT值的影响,不同扫描条件下图像SNR的变化、图像CT值的关系以及图像噪声与辐射剂量的相关性。方法 配制碘浓度为0.5～50.0 mg/mL(以0.5 mg/mL递增)的100份样本。将样本按顺序装入量均为4 mL的100个注射器,每25个为1组,将其用胶带等间隔固定在CT校准专用水模上。采用不同管电流(50 mA、100 mA、200 mA、280 mA)及管电压(70 kV、80 kV、100 kV、120 kV、140 kV),两两结合共20种扫描方式行轴面扫描。测量不同浓度样本在不同扫描条件下的CT值以及各种扫描条件下的图像噪声、SNR和辐射剂量。采用方差分析比较不同管电流、管电压条件下CT值和SNR的差异,采用Pearson线性相关分析评价不同扫描条件下CT值以及图像噪声和辐射剂量的相关性,并用线性回归得到回归方程及相关系数,根据图像噪声与辐射剂量的关系曲线计算不同管电压时曲线的交汇点。结果 管电流固定,不同管电压下图像CT值的差异均有统计学意义(P均<0.05);管电压固定,不同管电流下图像CT值的差异均无统计学意义(P均>0.05)。不同扫描条件下图像CT值呈线性相关(R~2=0.973～0.999),并以120 kV扫描的CT值为基准,得到其他管电压扫描下图像CT值的转化公式。不同管电压下图像噪声与辐射剂量呈反比,并根据相关方程得到不同管电压下图像噪声和辐射剂量的关键点。结论 管电压对图像CT值、SNR有影响,可以根据图像噪声和辐射剂量的相关关键点调整管电压,以获得保证图像质量并降低辐射剂量的优化扫描方案。更多还原

【Abstract】 Objective To investigate the impact of tube current and tube voltage changes on imaging CT attenuation,the SNR and CT attenuations under different scanning conditions,and the correlation between image noise and radiation dose.Methods A total of100 saline solutions with decreasing dilution of contrast medium,in which concentration was between 0.5 mg/mL and 50.0 mg/mL with the interval of 0.5 mg/mL were produced.Each group of the 25 syringes with a 4 mL sample was fixed on a cylindrical CT calibrated water phantom with an equal distance using the tape.CT scans were performed with a total of 20 scanning methods of the combination of the different tube current(50 mA,100 mA,200 mA,280 mA) and tube voltages(70 kV,80 kV,100 kV,120 kV,140 kV).All of the CT attenuations,image noise,SNR and radiation dose were measured and recorded.Compared the difference of CT attenuations and SNR under different scanning tube current and tube voltage using one-way ANOVA.The Pearson correlation analysis was used to analyze the relationship between CT attenuation,image noise and radiation dose in different scanning conditions,and linear correlation equations were calculated and showed by regression analysis.According to the statistical relation curve of the image noise and the radiation dose,the intersection point of the related curves was calculated at different tube voltages.Results The difference of CT attenuations between different tube voltages was statistically significant(all P<0.05) when the tube current was fixed,while there was no significant difference in CT attenuations between different tube currents when the tube voltage was fixed(all P>0.05).The CT attenuations of the images were linearly correlated(R~2=0.973-0.999) under different scanning conditions.Taking the CT attenuations of 120 kV scan as a reference,the conversion formula of CT attenuations of other tube voltages scan was obtained.Image noise and radiation dose were inversely proportional under different tube voltage scanning,and key points of image noise and radiation dose were obtained according to the related equations.Conclusion The tube voltage has an effect on the CT attenuations and SNR,the tube voltage can be adjusted according to the key points of the image noise and radiation dose to obtain an optimized scanning scheme that ensures image quality and reduces the radiation dose.更多还原