Correlation between age and head diameters in the paediatric patients during CT examination of the head

An estimate of patient dose, patient size should be used to normalise the output dose of CT machine in the terms of volume CT dose index, CTDI_vol. There are two metrics to characterise the patient size, i.e. the effective diameter (D_eff) and the water-equivalent diameter (D_w). These two metrics could be estimated by patient age. However, to date, relationships between the age and head patient size (D_eff and D_w) have not been established for the pediatric patients. The aim of this study was to establish the relationships between the age and head patient size (D_eff and the D_w) as the basis for calculating the size-specific dose estimate (SSDE) for paediatric head CT examination. The data were retrospectively collected from serial images of the CT head in the DICOM file from one hundred and thirteen paediatric patients aged 0-17 years (63 male and 50 female patients) underwent head CT examinations. The patient’s sizes (D_eff and D_w) were calculated from the patient’s images using the IndoseCT version 15a software. The D_eff and D_w values were correlated with age of patients using regression analysis. It was found that patient size (D_eff and D_w) correlated well with the age of the patient with R² more than 0.8. The size of the D_w is bigger than the D_eff. The D_eff values for male patients are 12.38 to 16.21 cm, and D_w values are 11.96 to 18.16 cm, respectively. For female patients, the values of D_eff are from 11.54 to 16.87 cm, and the values of D_w are from 11.60 to 17.86 cm, respectively.