Diagnostic reference levels for chest computed tomography in children as a function of patient size.

ABSTRACT

BACKGROUND: Radiation exposures from computed tomography (CT) in children are inadequately studied. Diagnostic reference levels (DRLs) can help optimise radiation doses. OBJECTIVE: To determine local DRLs for paediatric chest CT performed mainly on modern dual-source, multi-slice CT scanners as a function of patient size. MATERIALS AND METHODS: Five hundred thirty-eight chest CT scans in 345 children under 15 years (y) of age (median age 8 y, interquartile range [IQR] 4-13 y) performed on four different CT scanners (38% on third-generation and 43% on second-generation dual-source CT) between November 2013 and December 2020 were retrospectively analysed. Examinations were grouped by water-equivalent diameter as a measure of patient size. DRLs for volume CT dose index (CTDIvol) and dose-length product (DLP) were determined for six different patient sizes and compared to national and European DRLs. RESULTS: The DRLs for CTDIvol and DLP are determined for each patient size group as a function of water-equivalent diameter as follows (I) < 13 cm (n = 22; median age 7 months) 0.4 mGy, 7 mGy·cm; (II) 13 cm to less than 17 cm (n = 151; median age 3 y) 1.2 mGy, 25 mGy·cm; (III) 17 cm to less than 21 cm (n = 211; median age 8 y) 1.7 mGy, 44 mGy·cm; (IV) 21 cm to less than 25 cm (n = 97; median age 14 y) 3.0 mGy, 88 mGy·cm; (V) 25 cm to less than 29 cm (n = 42; median age 14 y) 4.5 mGy, 135 mGy·cm; (VI) ≥ 29 cm (n = 15; median age 14 y) 8.0 mGy, 241 mGy·cm. Compared with corresponding age and weight groups, our size-based DRLs for DLP are 54% to 71% lower than national and 23% to 85% lower than European DRLs. CONCLUSION: We developed DRLs for paediatric chest CT as a function of patient size with substantially lower values than national and European DRLs. Precise knowledge of size-based DRLs may assist other institutions in further dose optimisation in children.