Abstract
Background
Size-specific dose estimate is gaining increased acceptance as the preferred index of CT dose in children. However it was developed based on non-clinical data.
Objective
To compare the accuracy of size-specific dose estimate (SSDE) based on geometric and body weight measures in pediatric chest and abdomen CT scans, versus the more accurate \( \overline{\mathrm{SSDE}} \) (mean SSDE based on water-equivalent diameter).
Materials and methods
We retrospectively identified 50 consecutive children (age <18 years) who underwent chest CT examination and 50 children who underwent abdomen CT. We measured anteroposterior diameter (DAP) and lateral diameter (DLAT) at the central slice (of scan length) of each patient and calculated DAP+LAT (anteroposterior diameter plus lateral diameter) and DED (effective diameter) for each patient. We calculated the following in each child: (1) SSDEs based on DAP, DLAT, DAP+LAT, DED, and body weight, and (2) SSDE based on software calculation of mean water-equivalent diameter (\( \overline{\mathrm{SSDE}} \) adopted standard within our study). We used intraclass correlation coefficient (ICC) and Bland–Altman analysis to compare agreement between the SSDEs and \( \overline{\mathrm{SSDE}} \).
Results
Gender and age distribution were similar between chest and abdomen CT groups; mean body weight was 37 kg for both groups, with ranges of 6–130 kg (chest) and 8–107 kg (abdomen). SSDEs had very strong agreement (ICC>0.9) with \( \overline{\mathrm{SSDE}} \). SSDEs based on DLAT had 95% limits of agreement of up to 43% with \( \overline{\mathrm{SSDE}} \). SSDEs based on other parameters (body weight, DAP, DAP+LAT, DED) had 95% limits of agreement of up to 25%.
Conclusion
Differences between SSDEs calculated using various indications of patient size (geometric indices and patient weight) and the more accurate \( \overline{\mathrm{SSDE}} \) calculated using proprietary software were generally small, with the possible exception for lateral diameter, and provide acceptable dose estimates for body CT in children.
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Karmazyn, B., Ai, H., Klahr, P. et al. How accurate is size-specific dose estimate in pediatric body CT examinations?. Pediatr Radiol 46, 1234–1240 (2016). https://doi.org/10.1007/s00247-016-3604-0
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DOI: https://doi.org/10.1007/s00247-016-3604-0