To investigate the value of the size-specific dose estimate (SSDE) on dose estimations of children's head CT scans.

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 (CTDI_vol)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 CTDI_vol) were compared for different groups, and the correlation of HC with f₂₉₃ and SSDE₂₉₃ was analyzed.

There was an overestimation of f₂₂₀ by 11.11% (t=252.61, P<0.05) compared withf₂₉₃. 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 CTDI_vol. 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 CTDI_vol. 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 CTDI_vol. Furthermore, HC was highly correlated with f₂₉₃ and SSDE₂₉₃ (r²=0.88 and 0.76, respectively, P< 0.05).

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 CTDI_vol. 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.

Size-specific dose estimate; Children; Head; Computed Tomography