低剂量CT胸部体检中噪声指数的设定

摘要

目的 探讨自适应统计迭代重建(ASIR)技术在胸部低剂量检查中噪声指数(NI)的最佳值,以减少患者的辐射剂量.资料与方法 根据NI的不同将1200例中老年健康体检者随机分成4组,每组300例,A组:NI=20;B组:NI=25;C组:NI=30;D组为常规组NI=14,并结合ASIR技术对轴位图像质量进行阅读、评价,根据图像质量及疾病的显示满意程度进行评分,并记录结果.结果 各组图像的主观评分分别为A组(3.53±0.43)分、B组(3.28±0.32)分、C组(3.12±0.18)分、D组(5.00±0)分;4组均＞3分,可用于诊断;体重指数分别为(24.39±3.09) kg/m2、(25.49±2.45) kg/m2、(25.53±3.21) kg/m2、(25.55±2.28) kg/m2;层数分别为60.64±6.38、64.42±5.71、61.77±6.45、62.32±6.15,4组间比较差异无统计学意义(P＞0.05);有效剂量(ED)分别为(1.66±0.84) mSv、(1.11±034) mSv、(0.88±030) mSv、(5.99±1.37) mSv,4组间两两比较差异均有统计学意义(均P＜0.05);C组ED最低,比D组辐射剂量低85％、比A组低47％、比B组低21％.结论 结合ASIR技术,选择NI=30既能保证图像质量满足诊断需求,又能有效降低辐射剂量,是一种较好的扫描方案.%Purpose To explore the optimal value of noise index (NI) of adaptive statistical iterative reconstruction (ASIR) in low-dose chest examination,so as to reduce the radiation dose of patients.Materials and Methods 1200 mid-age and elderly healthy individuals were randomly divided into 4 groups according to the NI difference,with 300 in each group,group A:NI=20;group B:NI=25;group C:NI=30;group D (the normal control group):NI=14.Combined with AS IR technology,the quality of the axial image was reviewed and evaluated,and the score of each subject was given and recorded based on the quality of the image and the matching degree with the disease it indicated.Results The subjective scores of images in each group were:group A (3.53±0.43),group B (3.28±0.32),group C (3.12±0.18) and group D (5.00±0),respectively.The scores of these 4 groups were all above 3,which could be used for diagnosis.The body mass index was (24.39 ± 3.09) kg/m2,(25.49 ± 2.45) kg/m2,(25.53 ± 3.21) kg/m2 and (25.55 ± 2.28) kg/m2,respectively.The number of layers was 60.64 ± 6.38,64.42 ± 5.71,61.77 ± 6.45 and 62.32±6.15,respectively,and there was no statistically significant difference between these 4 groups (P＞0.05).The effective dose (ED) was (1.66± 0.84) mSv,(1.11 ± 0.34) mSv,(0.88±0.30) mSv and (5.99± 1.37) mSv,respectively,and the differences between any two groups were all statistically significant (P＜0.05).ED of group C was the lowest,85％ lower than group D,47％ lower than group A,and 21％ lower than group B.Conclusion Using ASIR technology,setting NI=30 can ensure that the image quality meet the needs of diagnosis,and also effectively reduce the radiation dose,which is a preferable scanning scheme.