Preliminary study on calculating size-specific dose estimate values based on age in children′s head / 中华放射医学与防护杂志

ABSTRACT

Objective:To investigate the feasibility of size-specific dose estimate of head based on pediatric patients′ age.Methods:A retrospective study was conducted on plain head CT scans of 210 patients in Tianjin Children′s Hospital from January to March in 2022. The volume CT dose index (CTDI vol) values, age and sex of the patients were recorded. The anteroposterior diameter (AP) and lateral diameter(LAT), aera and CT value in the middle slice of the scan region were measured on the workspace. According to the AAPM reports 220 and 293, the water equivalent diameter ( DW) of head, size-specific conversion factors ( fmeasuredH16), and size-specific dose estimate (SSDE measured) were calculated. The effective diameter ( Deff; WHO) was calculated for male and female individuals using the ralationship between the standard head circumference and age of children provided by World Health Organization (WHO). The effective diameter ( Deff; WHO) was converted into a water equivalent diameter ( DW; WHO), using a correlation established from the Deff and DWwhich were measured in 210 image sets of male and female patients. Then the corresponding fWHOH16 and SSDE WHO of head can be calculated. The correlation between DW and DW; WHO, fmeasuredH16 and fWHOH16, the correlation and consistency between SSDE measured and SSDE WHO, and the conversion relationship between age and fWHOH16 were analyzed for male and female patients. Results:A significant correlation were found between the measured DW and DW; WHO(female r=0.917, P<0.01; male r=0.873, P<0.01), fmeasuredH16 and fWHOH16(female r=0.916, P<0.01; male r=0.883, P<0.01), SSDE measured and SSDE WHO( r=0.991, P<0.01; male r=0.992, P<0.01). The Bland-Altman test indicated that there was good coherence between SSDE measured and SSDE WHO. Maximal mean root-mean-square errors of SSDE measured and SSDE WHO were 5.61% in female and 5.25% in male. The conversion relationship between fWHOH16 and patient age in different genders was obtained by curve fitting. Conclusion:The SSDE of head in pediatric patients can be estimated simply and accurately by directly using the patient′s age.