评估80 kVp结合ASIR-V腹部CT血管成像：图像质量、辐射剂量及碘摄入量研究

ASIR-V and 80 kVp in abdominal CT angiography：evaluation of image quality，radiation dose，and iodine intake

摘要:

目的：探讨应用80 kVp行腹部CT血管成像（CT angiography，CTA）扫描对辐射剂量、碘摄入量及图像质量的影响。方法：应用GE Revolution CT对49例（20≤BMI≤23）病人行全腹部CTA检查，按管电压分为2组，A组27例，采用80 kVp、50%ASIR-V、自动mA、NI采用设备推荐值、层厚1.25 mm、HD扫描模式、Stnd重建、探测器宽度80 mm、扫描时间0.5 s；B组22例，采用120 kVp、余参数同A组。对比剂注射方案：A、B 2组均采用碘海醇（350 mgI/mL）对比剂。A组为300 mgI/kg，流速4 mL/s，B组为500 mgI/kg，流速5 mL/s。采用自动跟踪触发，阈值为220 HU。分别测量A、B两组的腹主动脉、腹腔干、肝总动脉、脾动脉、肠系膜上动脉及同层面竖脊肌的CT值和SD值的均值；评价图像[容积再现（volume rendering，VR）、最大密度投影（maxi－mum intensity projection，MIP）]质量。计算腹主动脉的CNR、SNR；统计两组的CTDIvol、DLP及碘摄入量。采用SPSS软件进行统计学分析。结果：A、B 2组腹部CTA图像评分为（4.58±0.51）分、（4.32±0.58）分，无统计学差异（P＞0.05），?资值分别为0.915、0.946；A、B两组腹主动脉CT值分别为（584.09±63.54） HU、（407.89±60.78） HU，肝总动脉CT值为（503.22±58.72） HU、（368.57±45.31） HU，脾动脉CT值为（486.44±74.47） HU、（371.88±49.55） HU，肠系膜上动脉的CT值为（535.23±54.94） HU、（387.83±55.85） HU，2组所测动脉的CT值差异均有统计学意义（P＜0.05）。A组腹主动脉SNR、CNR均高于B组（P＜0.05）；A、B 2组的CTDIvol分别为（3.34±0.22） mGy、（8.78±0.93） mGy，DLP分别为（172.77±13.75） mGy·cm、（438.30±58.23） mGy·cm，差异均有统计学意义，A组CTDIvol较B组降低61.96%、DLP降低60.58%；A、B组每例患者检查总碘摄入量分别为300 mgI/kg、500 mgI/kg，A组总碘摄入量较B组降低39.67%。结论：应用80 kVp低管电压（20 kg/m2≤BMI≤23 kg/m2）行腹部CTA扫描，辐射剂量、对比剂摄入量明显降低，腹主动脉及其主要分支图像CNR和SNR有较大提高。

Abstract:

Objective：To examine the effects of 80 kVp on radiation dose，iodine intake，and image quality for abdominal computed to－mography angiography（CTA）. Methods：Abdominal CTA was performed in 49 patients（20≤BMI≤23） using GE Revolution CT. The patients were divided based on tube voltage into group A（n=27，80 kVp） and group B（n=22，120 kVp）. With the exception of kVp，all scanning parameters in the two groups were the same：automatic mA，50% ASIR-V，default NI，1.25 mm thickness，HD mode，Stnd reconstruction，80 mm detector width，and 0.5 s scan time. Iohexol contrast agent（350 mgI/mL） was administered at 300 mgI/kg（4 mL/s） in group A and at 500 mgI/kg（5 mL/s） in group B，and was automatically tracked at a threshold of 220 HU. The mean CT and SD values of the abdominal aorta，abdominal trunk，common hepatic artery，splenic artery，superior mesenteric artery，and erector spinae at those levels were measured. Image quality（volume rendering and maximum intensity projection），contrast-to-noise ratio（CNR） and signal-to-noise（SNR） of the abdominal artery，volume CT dose index（CTDIvol），dose-length product（DLP），and total iodine intake were determined and compared between the two groups using the SPSS software. Results：There was no significant difference in the CTA image score between group A（4.58±0.51；κ=0.915） and group B（4.32±0.58，κ=0.946）（P>0.05）. The CT values of the abdominal aorta，common hepatic artery，splenic artery，and superior mesenteric artery were signifi－cantly higher in group A（584.09±63.54 HU，503.22±58.72 HU，486.44±74.47 HU，and 535.23±54.94 HU，respectively） than in group B（407.89±60.78 HU，368.57±45.31 HU，371.88±49.55 HU，and 387.83±55.85 HU，respectively）（all P<0.05）. The SNRs and CNRs were also significantly higher in group A than in group B（both P<0.05）. Compared with group B，group A had significantly lower CTDIvol（3.34±0.22 mGy vs. 8.78±0.93 mGy；61.96% reduction） and DLP（172.77±13.75 mGy·cm vs. 438.30±58.23 mGy·cm；60.58% reduction）. The total iodine intake of each patient was reduced by 39.67% in group A（300 mgI/kg） compared with group B （500 mgI/kg）. Conclusion：Abdominal CTA at a low tube voltage of 80 kVp（20 kg/m2≤BMI≤23 kg/m2） significantly reduces the radiation dose and contrast agent intake in patients，and improves CNR and SNR of the abdominal aorta and its major branches.