Abstract：Objective To compare the difference Size specific dose estimate (SSDE) between effective diameter (De) and water
equivalent diameter (Dw) in children’s chest CT examination and find out a simple and intuitive method to reflect the radiation dose.
Methods A prospective study of 118 children undergoing chest CT scans were enrolled and divided into group A (37 children aged 0-3
years), group B (39 children aged 4-7 years) and group C (42 children aged 8-16 years). CTDIVOL was obtained from the workstation
dose report. The anteroposterior diameter and left and transverse diameter of thorax were measured on the middle CT image, and
the De was calculated. SSDEDe was obtained according to the conversion factor fDe corresponding to De. The ellipse of interest was
drawn on every CT image. The ellipse covered all anatomical structures of cross-sectional images. The average CT values of ellipse
area and ellipse area were recorded, and the was calculated. According to the conversion factor fDw corresponding to Dw, SSDEDw
was obtained. Then, variance analysis was used to compare De, Dw, fDe, fDw, SSDEDe and SSDEDw among groups, and the paired t test
was used to compare the diameter, conversion factor and SSDE under two SSDE calculation methods in each group. Results There
were significant differences in De, Dw, fDe, fDw, SSDEDe and SSDEDw among groups, and there were significant differences between
every two groups (P<0.05). With the increase of age, the De and Dw increased, while the fDe, fDw, SSDEDe and SSDEDw decreased. In
group A, De was 10.5% higher than Dw, fDe 13.5% lower than fDw, SSDEDe 13.6% lower than SSDEDw; in group B, De was 10% higher
than Dw, fDe 15.5% lower than fDw, SSDEDe 16% lower than SSDEDw; in group C, De was 13.2% higher than Dw, fDe 17.8% lower
than fDw, SSDEDe 18.1% lower than SSDEDw; all of these differences were statistically significant (P<0.05). SSDEDe and SSDEDw were
positively correlated with SSDEg in group A (r=0.90, 0.91, P<0.05); SSDEDe and SSDEDw were positively correlated with SSDEg
in group B (r=0.89, 0.92, P<0.05); SSDEDe and SSDEDw were positively correlated with SSDEg in group C (r=0.88, 0.90, P<0.05).
Conclusion SSDEDw can more accurately assess the radiation dose of children; SSDEDw at the central image is a simple and accurate
representative parameter for reflecting radiation dose of children.
张楠，边传振，王颖，姜辉. 不同体型特异性剂量估算值在儿童胸部CT的应用[J]. 中国医疗设备, 2020, 35(3): 88-91.
ZHANG Nan, BIAN Chuanzhen, WANG Ying，JIANG Hui. Application of Different Size-Specific Dose Estimate in Children’s Chest CT. China Medical Devices, 2020, 35(3): 88-91.