比较头颈部CTA常规扫描与低对比剂、能谱单能量扫描的图像质量、辐射剂量

Comparison of Image Quality and Radiation Dose between Conventional Scans and Single-Energy Spectral Scans with Low-Contrast Agents in Head and Neck CTA

目的探讨能谱CT联合低对比剂用量在头颈部CT血管造影(CTA)中的图像质量和辐射剂量。方法前瞻性选取90例行头颈CTA检查的患者,根据扫描方式和对比剂注射方案不同随机分成A组(120 kV混合能量CT+常规对比剂剂量)、B组(能谱CT 60 keV单能量重组+常规对比剂剂量)、C组(能谱CT 60 keV单能量重组+低对比剂剂量组)。利用宝石能谱成像(GSI)能谱分析软件(Volume Viewer 15.0 Ext.2),分别重组B、C组60 keV最佳单能量图像,对A、B、C三组图像分别进行容积再现(VR)、最大密度投影(MIP)和曲面重组(CPR)后处理。分别测量主动脉弓、颈总动脉起始处、颈内动脉起始处、大脑中动脉M1段及乳头层面胸大肌CT值和标准差(SD)值。计算每组图像各动脉血管平均值和信噪比(SNR)、对比噪声比(CNR)。由两名放射科医师分别对三组图像采用5分法进行主观评分。记录剂量长度乘积(DLP)、有效辐射剂量(ED)和碘摄入量。采用单因素方差分析和Kruskal-Wallis检验进行统计学分析。采用SPSS 22.0软件进行数据分析。定量资料分别采用卡方检验、单因素方差分析,组间比较采用Bonferroni检验。图像质量主观评分用Kruskal-Wallis检验比较,采用Kappa检验对两位放射科医师图像质量主观评分一致性进行分析。P<0.05表示差异有统计学意义。结果B组、C组的DLP和ED值均低于A组,差异具有统计学意义(P<0.05),B、C组间无统计学差异。C组的碘对比剂用量较A、B组低,差异具有统计学意义(P<0.05)。图像客观评价中,B、C组靶血管CT值均高于A组,差异具有统计学意义(P<0.05)。B组的SNR高于A组,差异有统计学意义(P<0.05)。B组、C组的CNR均高于A组,B组的CNR最高,三组间差异均有统计学意义(P<0.05)。B、C组主观评分均高于A组(P<0.05),差异具有统计学意义,B组与C组差异无统计学意义(P>0.05)。两名医师对三组图像评价结果的一致性较好(Kappa=0.812)。结论低对比剂、60 keV最佳单能量重组图像能够明显降低辐射剂量和对比剂用量、提高图像质量。

Objective To explore the image quality and radiation dose of using energy spectrum single-energy imaging combined with extremely low contrast agent dose technology in head and neck CTA.Methods A prospective selection of 90 patients underwent head and neck CTA examinations were randomly divided into three groups according to different scanning methods and contrast agent injection schemes:group A(traditional 120 kV CT and conventional contrast agent dose group),group B(energy spectrum CT and conventional contrast agent dose group),and group C(energy spectrum CT and extremely low contrast agent dose group).After scanning the energy spectrum group,the best single-energy image(60 keV),iodine base map and calcium base map were reconstructed.Measured the attenuation values and standard deviations of on the images of aortic arch,common carotid artery,internal carotid artery,middle cerebral artery and muscles on the same plane of these vessels in 3 groups.The signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of each vessel were calculated.The image quality was evaluated by two radiologists using a 5-point method.The dose length product(DLP),effective radiation dose(ED)and iodine intake were recorded.One-way ANOVA and Kruskal-Wallis test were used for statistical analysis.Results In the objective image evaluation,the CT values of vessels in group B and group C were higher than those of group A(P<0.05),there was no statistically significant difference between groups B and C(P>0.05);The comparison of SNR and CNR between group B and C were not statistically significant(P>0.05),but they were all higher than group A(P<0.05).In the subjective image evaluation,the image quality of group A,B,and C met the clinical diagnosis requirements,and the subjective scores of the B and C groups were higher than those of group A(P<0.05).The difference between the B and C groups is not statistically significant(P>0.05).The radiation doses of group B and C were significantly lower than group A(P<0.05),but the difference between group B and C was not statistically significant(P>0.05).The iodine intake of group C was 46%lower than that of group A and 47%lower than that of group B,the difference was statistically significant(P<0.05).Conclusion The best single-energy imaging of energy spectrum CT combined with extremely low contrast agent dose in head and neck CTA can not only obtain high-quality images,but also significantly reduce the patient’s radiation dose and iodine intake,which is worthy of clinical application.