下肢动脉计算机断层成像血管造影的超低剂量成像分析

Study of Ultra-low Dose Imaging in Computed Tomography Angiography of Lower Extremity Arteries

目的评估采用80 kV管电压、50 mA管电流的扫描方式并结合自适应迭代重建(ASiR-V)的下肢动脉计算机断层成像血管造影(CTA)扫描方案的图像质量和辐射剂量。方法收集2022年1月—2022年6月80例行下肢动脉CTA扫描患者的临床资料,随机分为标准化低剂量扫描组(标准化组,n=40)和超低剂量扫描组(超低剂量组,n=40),标准化组采用100 kV管电压和自动调节管电流,图像重建采用滤波反投影(FBP)算法;超低剂量组采用80 kV管电压及50 mA固定管电流,图像重建采用50%权重的ASiR-V(ASiR-V 50%)算法。测量目标血管的CT值、信噪比(SNR)、对比噪声比(CNR),记录容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP),并对图像质量进行主观评分。结果超低剂量组各血管评估区的CT值均高于标准化组(P<0.05),且具有更高的SNR(P<0.05)和CNR(P<0.05)。超低剂量组的CTDIvol[(1.09±0.00)mGy vs(5.63±1.28)mGy,P<0.05]和DLP[(131.05±5.50)mGy·cm vs(714.94±189.23)mGy·cm,P<0.05]较标准化组明显降低,其中CTDIvol降低约81%。与标准化组比较,超低剂量组在腘下动脉节段具有更优的主观评分(P<0.05),其余节段差别无统计学意义(P>0.05)。结论采用80 kV低管电压、50 mA低管电流并结合ASiR-V 50%图像重建算法的超低剂量下肢CTA扫描方案,可有效降低辐射剂量,且保持较高的图像质量。

Objective The purpose of this study is to evaluate the image quality and radiation dose while applying 80 kV tube voltage,50 mA tube current combined with adaptive statistical iterative reconstruction(ASiR-V)in lower extremity computed tomography angiography(CTA),compared with the institutional standardized low dose protocol.Methods 80 subjects who underwent lower extremity CTA were included in this study from January 2022 to June 2022.All the participants were divided into two groups randomly.One was standardized group(n=40)and the other was ultra-low dose group(n=40).100 kV tube voltage,automatic tube current modulation and filtered back projection(FBP)were applied in the standardized group while the 80 kV,50 mA and 50%weight of ASiR-V(ASiR-V 50%)were used in the ultra-low dose group.For each subject,CT attenuation,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)were calculated by the formula,computed tomography dose index volume(CTDIvol)and dose length product(DLP)were recorded as well.The subjective scores of image quality were evaluated by two experts who are experienced in CT angiography.The independent t-test was performed for statistical evaluation,and P value<0.05 was set as significant difference.Result The CT attenuation,SNR and CNR in ultra-low dose group were significantly higher than those in standardized group.The CTDIvol in ultra-low dose group was approximately 81%lower than that in the standardized group[(1.09±0.00)mGy vs(5.63±1.28)mGy,P<0.05],as well as DLP[(131.05±5.50)mGy·cm vs(714.94±189.23)mGy·cm,P<0.05].Ultra-low dose group had the similar subjective image score with standardized group(P>0.05)in all segments except calf segment.Conclusion This ultra-low dose protocol by using 80 kV,50 mA and ASiR-V 50%could be applied in the lower extremity CT angiography to reduce the radiation dose with good image quality.