能谱CT双低剂量在下肢动脉CTA中的应用研究

目的：探讨使用低管电压和低浓度对比剂对下肢动脉CTA检查的图像质量和辐射剂量的影响。方法：行下肢动脉CTA的连续80例患者，随机分成两组，每组各40例。A组：管电压100kVp，对比剂使用威视派克（270mgI／mL）；B组：管电压120kVp，对比剂为欧乃派克（350mgI／mL）。图像重建使用自适应统计迭代算法（ASiR）。两组其它扫描参数相同。测量和计算图像最佳对比噪声比（CNR），噪声值（SD）和多处下肢动脉CT值的均值，计算每例患者的辐射剂量（ED）及平均碘摄入量（mgI／kg），由两位放射医师采用4分法评估图像质量，对2组间的上述指标进行统计学分析。结果：A组图像的CNR（15．23±2．10）高于B组（13．42±1．93），差异有高度统计学意义（t=4．02，P％0．001）。A组的图像噪声和图像质量评分分别为（9．45±1.04）HU和（3．64±0．49）分，B组为（9．38±0．97）HU和（3．52±0．48）分，差异均无统计学意义（P〉0．05）。A组下肢动脉平均CT值为（446．5±30．3）HU，高于B组的（375．1±24．6）HU，差异有高度统计学意义（t=11．57，P〈0．001）。A组辐射剂量（13．25±2．08）mSv]明显低于B组（22．43±3．67）mSv]，降低约40％（t=13．2，P〈0．001）。A组人均碘摄入量为（290．42±10．04）mgI／kg），显著低于B组的（363．34±12．34）mgI／kg（t=63．46，P〈0．001）。结论：能谱CT下肢动脉CTA使用低管电压及低浓度对比剂可以提供更好的图像对比噪声比，在保证诊断图像质量的同时明显地降低了辐射剂量，同时减少了患者的对比剂碘的摄入量。

Application of spectral CT with double low dose technique in lower limb CT angiography

Objective：To evaluate the impact of image quality and radiation dose with spectral CT using ＂double low technique＂ （low tube voltage and low concentration contrast agent） in lower extremity CT angiograpby （CTA）. Methods： 80 consecutive patients planned to undergo lower extremity CTA were randomly divided into 2 groups,with 40 patients in each group. The parameters were as follows：Group A,tube voltage as 100kVp, contrast agent as visipaque （270rag I/mL） ; Group B,tube voltage as 120kVp,contrast agent as omnipaque （350rag I/mL）. Using adaptive statistical iterative algorithm （ASiR） for image reconstruction,the other scanning parameters were the same. The optimal contrast to noise ratio （CNR）, standard deviation （SD） of noise and the mean CT values of different areas of lower extremity arteries were recorded. The radiation dose （ED） and the average intake of iodine （mgI/kg） were calculated. The image quality was evaluated by 2 radiologists with 4 point scale assessment and analyzed by SPSS statistical software for data Test. Results：The CNR of Group A was 15.23±2.10,which was higher than that of Group B （13.42±1.93） ,with significant statistic difference （t=4.02, P〈0. 001）. The image noise and image quality scores of Group A were （9.45±1.04）HU and （3.64±0.49） respectively, of Group B were （9.38±0.97）HU and （3.52±0.48） respectively,with no statistic significance （P〉0.05）. The mean CT value of lower extremity artery was （446.5 ±30.3）HU, which is higher than that in Group B （375. 1 ±24.6）HU], with significant statistic difference （t=11.57,P〈0. 001）. The radiation dose of Group＇A was significantly lower than that in group B （13.25±2.08）mSv vs （22.43±3.67）mSv],with significant statistic difference （t= 13.2,P〈0. 001）,the radiation dose was reduced by approximately 40%. The iodine contrast agent intake /person in Group A was （290. 42 ± 10.04）mg I/kg,wbich is significantly （t=63.46,P〈0. 001） lower than that in Group B （363.34±12.34）mg I/kg]. Conclusion：Spectral CT using low tube voltage technique （100kVp） and low concentration contrast （270mg I/mL） for lower extremity CTA could provide better image contrast to noise ratio, which could ensure diagnostic image quality while significantly reduce the radiation dose,and simultaneously reduce the intake of iodine contrast agent.