DU Qianni, Sui Xin, Song Wei, Song Lan, Xu Xiaoli
Department of Radiology,PUMC Hospital,CAMS and PUMC,Beijing 100730,China.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2017 Feb 20;39(1):28-33. doi: 10.3881/j.issn.1000-503X.2017.01.006.
Objective To assess the application of high-pitch CT pulmonary angiography (CTPA) at 70 kV tube voltage with 15 ml contrast medium using third-generation dual-source CT. Methods A total of 70 patients with clinically suspected pulmonary embolism were randomly divided into two groups: group A (n=35) underwent CTPA on conventional scanning mode (120 kV,80 ml contrast medium);and group B (n=35) underwent CTPA on high-pitch scanning mode at 70 kV tube voltage with 15 ml contrast medium. The CT values and standard deviations of the main pulmonary artery,apical segment of right upper pulmonary lobe (S1),and posterior basal segment of the right lower pulmonary lobe (S10),anterior thoracic air,and back muscles were measured. The signal to noise ratio (SNR),contrast to noise ratio (CNR),and effective dose (ED) were calculated. The overall image quality was evaluated by two blinded radiologists. The quality image was compared using non-parametric test on two independent samples. The potential differences in CT value,SNR,CNR,and ED were analyzed using the independent sample t-test. Results The CT values of main pulmonary artery [(300.62±77.54)HU vs.(332.80±102.80)HU;t=-1.53,P=0.13],S1 [(361.72±84.92)HU vs. (325.37±87.86)HU;t=1.81,P=0.08],and S10 [(359.54±89.61)HU vs. (318.26±87.19)HU;t=2.00,P=0.05] of right lung were not significantly different between group A and group B. The CNR of S1 (22.81±6.05 vs. 19.80±6.60;t=2.05,P=0.04) and S10 (22.65±6.37 vs. 19.28±6.63;t=2.23,P=0.03) of right lung in group A was significantly higher than in group B. The SNR of main pulmonary artery,S1,and S10 of right lung were not significantly different between group A and B. The subjective diagnostic quality values of group A and B were 1 (1,1) and 1 (1,1),respectively (Z=-0.08,P=0.93). The subjective diagnostic quality values evaluated by two radiologists showed excellent consistency(κ=0.87,P=0.01). The mean ED was 79% lower in group B [(0.92±0.23)mSv] than in group A [(4.33±1.80) mSv] (t=11.72,P=0.00).Conclusion Application of high-pitch mode in CTPA at 70 kV with 15 ml contrast medium using third-generation dual-source CT can remarkably reduce radiation dose without affecting image quality.
目的 评估使用第三代双源CT在70 kV管电压及15 ml对比剂条件下进行高螺距CT肺动脉造影（CTPA）的应用情况。方法 选取70例临床怀疑肺栓塞的患者，随机分为两组：A组（n = 35）采用常规扫描模式（120 kV，80 ml对比剂）进行CTPA检查；B组（n = 35）采用70 kV管电压及15 ml对比剂的高螺距扫描模式进行CTPA检查。测量主肺动脉、右上肺叶尖段（S1）、右下肺叶后基底段（S10）、胸廓前部空气及背部肌肉的CT值和标准差。计算信噪比（SNR）、对比噪声比（CNR）及有效剂量（ED）。由两名不知情的放射科医生评估整体图像质量。采用两独立样本非参数检验比较图像质量。使用独立样本t检验分析CT值、SNR、CNR及ED的潜在差异。结果 A组和B组右肺主肺动脉[（300.62±77.54）HU对（332.80±102.80）HU；t = -1.53，P = 0.13]、S1[（361.72±84.92）HU对（325.37±87.86）HU；t = 1.81，P = 0.08]及S10[（359.54±89.61）HU对（318.26±87.19）HU；t = 2.00，P = 0.05]的CT值差异无统计学意义。A组右肺S1（22.81±6.05对19.80±6.60；t = 2.05，P = 0.04）和S10（22.65±6.37对19.28±6.63；t = 2.23，P = 0.03）的CNR显著高于B组。A组和B组右肺主肺动脉、S1及S10的SNR差异无统计学意义。A组和B组的主观诊断质量值分别为1（1，1）和1（1，1）（Z = -0.08，P = 0.93）。两名放射科医生评估的主观诊断质量值显示出极好的一致性（κ = 0.87，P = 0.01）。B组的平均ED[（0.92±0.23）mSv]比A组[（4.33±1.80）mSv]低79%（t = 11.72，P = 0.00）。结论 使用第三代双源CT在70 kV及15 ml对比剂条件下进行CTPA时应用高螺距模式可显著降低辐射剂量且不影响图像质量。
