宝石能谱成像不同噪声指数肝脏CT血管造影联合不同浓度对比剂用于超重及肥胖患者

Hepatic CT angiography in overweight or obese patients based on gemstone spectral imaging with different noise indexes and concentrations of contrast agent

目的观察以宝石能谱成像(GSI)不同噪声指数(NI)及不同浓度对比剂对超重[24 kg/m^(2)≤体质量指数(BMI)<28 kg/m^(2)]或肥胖(BMI≥28 kg/m^(2))患者行肝脏CT血管造影(CTA)的图像质量、辐射剂量和碘摄入量,筛选最佳参数组合。方法将90例超重或肥胖患者随机分为A、B、C组3组,每组30例;以GSI行肝脏CTA,分别设置NI为7、11及15,对比剂浓度分别为370、350及320 mgI/ml。根据各组原始图像重建40~60 keV(间隔5 keV)单能量图像,分析各组内不同单能量图中肝动脉、门静脉和肝静脉的CT值、噪声[标准差(SD)]、对比度噪声比(CNR)及图像质量主观评分结果;比较最佳单能量图所见各参数组间差异,计算体型特异性剂量估算值(SSDE)和碘摄入量。结果各组40~60 keV单能量图像中,肝动脉、门静脉和肝静脉CT值及SD值均随keV增加而降低(P均<0.001);40 keV单能量图像中肝动脉、门静脉和肝静脉CNR及图像质量主观评分高于50~60 keV(P均<0.05)及55~60 keV图像(P均<0.05),均以40 keV为最佳单能量水平;3组最佳单能量图所示上述各参数差异均无统计学意义(P均>0.05)。B、C组SSDE和碘摄入量均低于A组(P均<0.05),C组SSDE和碘摄入量均低于B组(P均<0.05)。结论基于GSI采用高NI(15)联合低浓度碘对比剂(320 mgI/ml)可在保证图像质量的前提下降低超重及肥胖患者肝脏CTA的辐射剂量和碘摄入量。

Objective To observe the image quality,radiation dose and iodine intake of hepatic CT angiography(CTA)based on gemstone spectral imaging(GSI)with different noise indexes(NI)and concentrations of contrast agent in overweight(24 kg/m^(2)≤body mass index[BMI]<28 kg/m^(2))or obese(BMI≥28 kg/m^(2))patients,and to screen the best combination of scanning parameters.Methods Ninety overweight or obese patients who would undergo hepatic CTA were prospectively collected and randomly divided into A,B and C group(each n=30),with NI of 7,11,15 and iodine concentrations of 370,350 and 320 mgI/ml,respectively.The single-energy images at 40—60 keV(5 keV interval)were reconstructed from the original images.CT value,noise(standard deviation[SD]value),contrast-to-noise ratio(CNR)and subjective score of hepatic artery,portal vein and hepatic vein on different single-energy images were analyzed to screen the optimal single-energy image of each group.The above parameters on the optimal single-energy images were compared among groups,and the size-specific dose estimates(SSDE)and iodine intake were analyzed.Results CT and SD values of hepatic artery,portal vein and hepatic vein in 40—60 keV single-energy images decreased with the increase of keV in all 3 groups(all P<0.001).CNR and subjective scores of hepatic artery,portal vein and hepatic vein on 40 keV single-energy images were all higher than those on 50—60 keV(all P<0.05),and CNR and subjective scores of hepatic artery,portal vein and hepatic vein on 45 keV single-energy images were higher than those on 55—60 keV(all P<0.05),indicating that 40 keV was the optimal single-energy level.No significant difference of CT,SD,CNR nor subjective scores of hepatic artery,portal vein and hepatic vein on the optimal single energy images was found among 3 groups(all P>0.05).SSDE and iodine intakes of B and C groups were lower than those of group A,and of group C were lower than those of group B(both P<0.05).Conclusion Based on GSI,high NI(15)combined with low concentration contrast agent(320 mgI/ml)could reduce radiation dose and iodine intake and ensure image quality of hepatic CTA of overweight or obese patients.