Setting of Noise Index in Low-dose Chest CT Examination / 中国医学影像学杂志

ABSTRACT

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 ANI=20;group BNI=25;group CNI=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 weregroup 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.