Effect of noise index and body mass index on radiation dose and image quality in low dose chest CT scanning in children

YU Caifeng; SHAO Changchun; JIANG Jun; DING Jiangpeng; MAO Lilin

doi:10.19300/j.2025.L21480

Abstract：Objective To investigate the effects of noise index(NI)and body mass index(BMI)on radiation dose and image quality in low dose chest CT scanning in children.Methods A total of 689 children aged 1 to 10 years were prospectively enrolled,with BMI ranging from 10.62 to 22.40 kg/m2(mean BMI:15.36±3.26 kg/m2).Five different noise index(NI)levels were set(10,15,20,25,and 30),with 124,129,166,202,and 68 children in each respective group.The children were divided into three BMI groups based on BMI thresholds of 14 and 16 kg/m2:low BMI group(BMI＜14 kg/m2,175 cases),medium BMI group(14-＜16 kg/m2,283 cases),and high BMI group(BMI≥ 16 kg/m2,231 cases).The impact of different NI and BMI on radiation dose and image quality of chest CT scans was analyzed,and the total scores of different combinations were calculated to determine the optimal combination.One-way analysis of variance(ANOVA)was used to compare radiation dose and image quality objective parameters in different BMI intervals across the five NI levels.Results When NI was 10 or 30,there were no significant differences in CT volume dose index(CTDIvol),dose length product(DLP),effective radiation dose(ED),standard deviation(SD)of CT value,and signal-to-noise ratio(SNR)among the different BMI groups(all P＞0.05).When the NI was 15,20,or 25,CTDIvol,DLP and ED increased progressively with BMI(all P＜0.05).There was no significant difference in SD and SNR(P＞0.05).In the low BMI group and medium BMI group,DLP and SNR total scores at NI=30 were higher than those at other NI levels.In the high BMI group,the DLP and SNR total score were higher at NI=25 compared to other NI levels.Within the same BMI group,the subjective score of image quality decreased gradually as the NI increase.Conclusion For children aged 1-10 years undergoing chest CT scans,selecting an appropriate NI based on the child's BMI can significantly reduce radiation dose while ensuring that image quality meets clinical diagnostic requirements.