Fig. 3.

Boxplots for CTDI-vol (a) and DLP (b) before and after the introduction of the HDM among age groups, as well as the dose reduction rate and statistical evaluation. a CTDI-vol (mGy). b DLP (mGy.cm). The mean CTDI-vol of head CT for all ages was 25.2 ± 4.5 mGy and 21.5 ± 6.9 mGy in the pre- and post-HDM groups, respectively, a 14.9% decrease before and after the introduction of the HDM. The mean DLPs of all head CTs were 504.5 ± 137.6 mGy.cm and 418.4 ± 152.9 mGy.cm in the pre- and post-HDM groups, respectively, with an overall reduction of 17.2% before and after the introduction of the HDM