低kVp、低浓度对比剂在双下肢CTA中的应用价值

Application of Low k V and Low Concentration of Iodine Contrast Medium in the Lower Extremity Artery Computed Tomography Angiography

目的探讨低kVp、低浓度对比剂在双下肢动脉CT血管造影（CTA）中的应用价值。方法搜集临床怀疑下肢动脉疾病的患者136例,随机分成两组：A组68例应用肘静脉注射常用浓度（350 mg I/ml）对比剂90-100ml,进行常规CT扫描（120 kVp）;B组68例患者应用肘静脉注射低浓度（270 mgI/ml）对比剂90-100 ml,进行低k Vp CT扫描（100 kVp）,两组均采用噪声指数（NI）为11的CARE Dose 4D自动mA调节技术;两组纳入条件均为体质量指数（BMI）〈25。主观图像质量评估由两名从事心血管影像诊断20年以上的专家进行盲法审阅,并对血管成像质量达成一致。两组图像的客观质量利用检测股动脉、大收肌的CT值,图像噪声（SD）,对比噪声比（CNR）来判断。统计两组的辐射剂量例如平均CT容积剂量指数（CTDIvol）,CNR和对比剂注射量。结果 A、B两组图像质量优良率分别为92.6%、91.2%,图像质量评分分别为：（3.6±0.6）分、（3.7±0.6）分;CTDIvol分别为（6.0±0.8）mGy、（4.0±0.9）mGy;对比剂注射剂量分别为（31.5±1.5）g、（26.7±1.6）g;有效mA分别为：（76.3±8.1）mA、（81.8±8.8）m ;SD分别为：10.0±1.7、11.6±2.4;CNR分别为：28.6±6.9、29.7±6.1。B组较A组CNR差异没有统计学意义（t=0.72,P=0.47）。B组较A组对比剂注射剂量差异具有统计学意义（t=18.47,P=0.00）。B组较A组CTA成像质量差异没有统计学意义（t=0.92,P=0.36）。B组较A组CTDIvol明显降低（t=13.91,P=0.00）,平均降低了33.3%。结论在下肢动脉CTA时,管电压100 kVp、自动mA、270 mgI/ml浓度对比剂,可以替代管电压120 kVp,自动mA、350 mgI/ml浓度对比剂的CTA,在碘对比剂注射量减少的情况下,辐射剂量明显下降。

Objective To investigate the application value of low kVp and low concentration of iodine contrast medium in the lower extremity artery computed tomography angiography（ CTA）. Methods 136 patients（ body mass index less than 25） with clinically suspected lower extremity arterial disease were randomly divided into two groups,each group included 68 cases,Noise Index（ NI） was 11,and automatic tube current control. Patients of group A were scanned with 120 kVp.Patients of group B were scanned with 100 kVp. The contrast medium for group A and group B were 350 mg/ml and 270 mg/ml respectively. The other scanning parameters are the same. Two experienced radiologists who engaged in cardiovascular imaging diagnosis more than 20 years double blindly assessed image quality subjectively. Objective evaluation index of the image quality included CT value of the femoral artery and adductor magnus,and image noise（ SD）. Average volume CT dose index（ CTDIvol）,contrast to noise ratio（ CNR） and contrast agent injection volume were calculated. Results The image quality excellent and good rate of group A and B were 92. 6% and 91. 2%,respectively. The subjective score of the image quality between the two groups showed no significant difference（ 3. 6 ± 0. 6 vs 3. 7 ± 0. 6,P 〉 0. 05）. Both the radiation dose and contrast medium dose of group A were lower than those of group B（ CTDIvol,6. 0 ± 0. 8 mGy vs 4. 0 ± 0. 9 mGy,P 〈 0. 001）,about 33. 3%,contrast medium dose（ 31. 5 ± 1. 5 g vs 26. 7 ± 1. 6 g,P 〈 0. 001）. Effective tube current group A were lower than those of group B（ 76. 3 ± 8. 1 vs 81. 8 ± 8. 8,P 〈 0. 001）. The SD value of the femoral artery of group A were higher than those of group B（ 10. 0 ± 1. 7 vs 11. 6 ± 2. 4,P 〈 0. 01）. The CNRs of the group A and the group B of the femoral artery showed no significant difference（ 28. 6 ± 6. 9 vs 29. 7 ± 6. 1,P 〉 0. 05）. Conclusion In the lower extremity artery CTA,double low protocol significantly reduced both radiation dose and contrast medium dose and provide similar image quality as routine high kVp and high concentration contrast medium protocol.