大螺距联合70 kV及迭代重建在下肢动脉CTA检查中的应用

Application of High Pitch Combined with 70 kV and Iterative Reconstruction in Lower Extremity Arterial CTA Examination

目的探讨大螺距联合70 kV及基于原始数据的迭代重建(SAFIRE)技术在下肢动脉CT血管造影(CTA)中应用的可行性。方法选取2021年8月至2022年1月在宜春市人民医院行下肢动脉CTA检查的60例患者为研究对象,依据随机数字表法分为常规组和研究组,每组30例。常规组下肢动脉CTA扫描方案:螺距0.6,管电压100 kV,滤波反投影算法,常规监测腹主动脉,对比剂总量为90~100 ml;研究组下肢动脉CTA扫描方案:螺距1.5,管电压70 kV,SAFIRE,监测层面放置于腘动脉水平,对比剂总量=患者体质量(kg)×1.1 ml/kg,其余扫描参数相同。测量并计算两组腹主动脉下段、股动脉中段、腘动脉段及胫后动脉中段血管感兴趣区的CT值、信噪比(SNR)及对比噪声比(CNR),记录患者的对比剂用量、扫描长度、容积剂量指数(CTDIvol)及剂量长度乘积(DLP),由2名资深影像医师对图像质量进行主观评分。结果两组腹主动脉下段和股动脉中段的CT值、SNR、CNR比较差异无统计学意义(P>0.05),研究组腘动脉段的CT值、SNR、CNR高于常规组(581±81比388±82、35.6±7.3比29.3±8.4、32.2±6.8比25.7±7.7)(P<0.01),胫后动脉中段的CT值、SNR、CNR均高于常规组(534±72比325±60、32.8±5.9比27.9±7.5、29.8±5.6比24.0±6.0)(P<0.01)。研究组对比剂用量少于常规组[(67±10)ml比(95±4)ml](P<0.01),CTDIvol、DLP低于常规组[(1.61±0.14)mGy比(5.62±0.39)mGy、(182±19)mGy·cm比(626±61)mGy·cm](P<0.01),两组扫描长度比较差异无统计学意义(P>0.05)。两组图像均能满足诊断,两组图像质量主观评价比较差异无统计学意义(P>0.05)。结论双源CT下肢动脉CTA检查应用大螺距1.5联合70 kV及迭代重建技术,在保证图像质量的情况下,能更好地减少对比剂用量及辐射剂量。

Objective To explore the feasibility of applying high pitch combined with 70 kV and sinogram-affirmed iterative reconstruction(SAFIRE)in CT angiography(CTA)of lower extremity arteries.Methods A total of 60 patients receiving lower extremity arterial CTA examination in Yichun People′s Hospital from Aug.2021 to Jan.2022 were included and randomly divided into a routine group and a research group,30 cases in each group.The scanning scheme of lower extremity arterial CTA for the routine group:pitch 0.6,tube voltage 100 kV,filtered back projection algorithm,routine monitoring of abdominal aorta,total contrast agent 90-100 ml;the scanning scheme of lower extremity arterial CTA of the research group:pitch 1.5,tube voltage 70 kV,SAFIRE,the monitoring plane was placed at the level of the popliteal artery,the total amount of contrast agent=patient weight(kg)×1.1 ml/kg,and other scanning parameters were the same.The CT value,signal-to-noise ratio(SNR),and contrast-to-noise ratio(CNR)of the region of interest of the lower abdominal aorta,middle femoral artery,popliteal artery and middle posterior tibial artery in the two groups were measured and calculated.The contrast agent dosage,scan length,volume dose index(CTDIvol)and dose length product(DLP)of the patients were recorded.And the image quality was subjectively scored by two senior radiologists.Results There was no significant difference in CT value,SNR and CNR of lower abdominal aorta and middle femoral artery between the two groups(P>0.05).The popliteal artery CT value,SNR,CNR of the research group were higher than those of the conventional group(581±81 vs 388±82,35.6±7.3 vs 29.3±8.4,32.2±6.8 vs 25.7±7.7)(P<0.01),the middle posterior tibial artery CT value,SNR and CNR in the research group were higher than those of the conventional group(534±72 vs 325±60,32.8±5.9 vs 27.9±7.5,29.8±5.6 vs 24.0±6.0)(P<0.01).The contrast agent dosage in the research group was less than that in the conventional group[(67±10)ml vs(95±4)ml](P<0.01).CTDIvol and DLP were lower than those in the conventional group[(1.61±0.14)mGy vs(5.62±0.39)mGy,(182±19)mGy·cm vs(626±61)mGy·cm](P<0.01).There was no significant difference in scan length between the two groups(P>0.05).The images of both groups could meet the diagnosis requirement,and there was no significant difference in the subjective evaluation of image quality between the two groups(P>0.05).Conclusion Under the condition of ensuring image quality,the application of high pitch 1.5 in dual source CT combined with 70 kV low tube voltage and iterative reconstruction technology in lower extremity arterial CTA examination can effectively reduce contrast agent consumption and radiation dose.