儿童头部CT体型特异性辐射剂量评价

Size-specific dose estimations in children′s head CT scans

目的探讨体型特异性辐射剂量(SSDE)在儿童头部CT辐射剂量评估的应用价值。方法回顾性收集2019年1-9月于华中科技大学同济医学院附属协和医院GE Discovery CT750HD 64排机器上行头部CT平扫的252例儿童患者的图像资料,记录其容积CT剂量指数(CTDIvol),通过自主开发的软件测量头部中间扫描层面的头围、面积及CT值,利用美国医学物理学会(AAPM)293和220报告计算水等效直径(WED)、体型转换系数(f293和f220)和吸收剂量(SSDE293和SSDE220)数值。根据头围大小按照四分法分成3组(<47.8、47.8~52.7、>52.7 cm),按照年龄分为4组(0~2、3~6、7~10和11~14岁)。比较不同组患者f220和f293、SSDE220和SSDE293、SSDE293和CTDIvol的差异性,并分析头围与f293、SSDE293的相关性。结果f220比f293高估11.11%(t=252.61,P<0.05),SSDE220较SSDE293高估10.31%(t=228.21,P<0.05),SSDE293较CTDIvol低估了9.60%(t=-31.34,P<0.05)。按头围分组时,所有组的SSDE220较SSDE293分别高估了8.41%、10.37%、11.57%(t=73.73、438.58、275.52,P<0.05);SSDE293较CTDIvol分别低估了1.30%、9.79%、14.61%(t=-1.91、-60.95、-47.64,P<0.05)。按年龄分组时,所有组的SSDE220较SSDE293分别高估了8.45%、10.00%、10.57%、11.36%(t=63.58、232.29、247.84、302.95,P<0.05);SSDE293较CTDIvol分别低估了1.49%、8.27%、10.63%、13.78%(t=-1.83、-28.27、-37.30、-49.80,P<0.05)。头围与f293、SSDE293具有较高的相关性(r2=0.88、0.76,P<0.05)。结论在儿童头部行CT扫描中,AAPM 293报告能更准确地评估其所受辐射剂量,CTDIvol会高估实际所接受的辐射剂量。AAPM 220报告相较AAPM 293报告会明显高估辐射剂量,并且头围与f293、SSDE293具有良好的相关性,利用头围能够准确估算SSDE,精确地评估儿童头部CT扫描时所接受的辐射剂量。

Objective To investigate the value of the size-specific dose estimate(SSDE)on dose estimations of children's head CT scans.Methods A retrospective study was conducted on plain head CT scans of 252 patients with the 64-row detector CT device of Discovery 750HD in the Union Hospital,Tongji Medical College,Huazhong University of Science and Technology from January to September in 2019.The volume CT dose index(CTDIvol)values were recorded.The head circumference(HC),area,and CT value were measured using a self-developed computer program,and the water equivalent diameter(WED),size-specific conversion factors(f293 and f220),and absorbed dose(SSDE293 and SSDE220)were calculated according to the AAPM reports 293 and 220.The patients were divided into three groups by the quartering meth odaccording to their HC(<47.8 cm,47.8-52.7 cm,>52.7 cm)and four groups based on their ages(0-2,3-6,7-10 and 11-14 years old).The difference between parameters(f220 and f293,SSDE220 and SSDE293、SSDE293 and CTDIvol)were compared for different groups,and the correlation of HC with f293 and SSDE293 was analyzed.Results There was an overestimation of f220 by 11.11%(t=252.61,P<0.05)compared with f293.SSDE220 was overestimated by 10.31%(t=228.21,P<0.05)compared with SSDE293,and SSDE293 was underestimated by 9.60%(t=-31.34,P<0.05)compared with CTDIvol.For the three HC groups,SSDE220 was overestimated by 8.54%,10.37%,and 11.57%(t=73.73,438.58,275.52,P<0.05)compared with SSDE293,and SSDE293 was underestimated by 1.30%,9.79%,and 14.61%(t=-1.91,-60.95,-47.64,P<0.05)compared with CTDIvol.For the four age groups SSDE220 was overestimated by 8.45%,10.00%,10.57%,and 11.36%(t=63.58,232.29,247.84,302.95,P<0.05)compared with SSDE293,and SSDE293 was underestimated by 1.49%,8.27%,10.63%,and 13.78%(t=-1.83,-28.27,-37.30,-49.80,P<0.05)compared with CTDIvol.Furthermore,HC was highly correlated with f293 and SSDE293(r2=0.88 and 0.76,respectively,P<0.05).Conclusions The radiation dose in children′s head CT scanning can be more accurately estimated according to the AAPM Report 293,while it can be overestimated by CTDIvol.Meanwhile,the CT radiation dose can be patently overestimated with the AAPM Report 220 compared with Report 293.HC is closely correlated with f293 and SSDE293 and it can be used to estimatee more accurately for SSDE and the radiation dose received by children during head CT scanning.