Size-based optimization of pediatric CT protocols: balancing radiation dose and image quality

This study investigated a water equivalent diameter (WED)-based tube voltage selection protocol for optimizing radiation dose and image quality in pediatric chest CT. A total of 100 pediatric patients were enrolled and retrospectively analyzed. They were divided into two groups based on the tube voltage used during chest CT: 100 kV and 120 kV. We set the region of interest (ROI) at the tracheal bifurcation in slice images of the lung, aorta, mediastinum, and humerus muscles, and calculated each organ's signal-to-noise ratio (SNR). We also calculated the central size-specific dose estimate (SSDEcenter), as well as the WED at the scan center and tracheal bifurcation. To normalize the CT scanner output, the ratio of SSDE to volume CT dose index (CTDIvol) and the ratio of SNR to CTDIvol of each target organ were calculated. We then evaluated the radiation dose and image quality of the two tube voltage protocols across different WEDs. Finally, the relationship between these ratios and WED was analyzed using fitting methods, and the advantageous WED ranges for the two protocols were determined based on curve intersections. The results demonstrated that SSDEcenter (coefficients of determination (R2) = 0.67) and SNR (R2 > 0.60) were correlated with WED. Under identical radiation output, the 100 kV protocol achieved a lower radiation dose for patients with WED< 22 cm, whereas the 120 kV demonstrated better dose optimization for those with WED>22 cm. For most organs except the aorta, SNR was higher at 100 kV when WED< 24 cm, with 120 kV proving superior above this threshold. The aorta consistently demonstrated better SNR at 120 kV regardless of WED. Based on these findings, we recommend 100 kV for patients with WED< 22 cm and 120 kV for those exceeding this threshold, guiding the optimization of pediatric chest CT protocol.