Clinical implications of lateral head mis-centering on eye lens dose in pediatric computed tomography examinations: a phantom study.

BACKGROUND AND AIM: Patient mis-centering during pediatric CT examinations can significantly affect radiation dose distribution, particularly to radiosensitive organs such as the eye lens. This study quantitatively evaluates the effect of lateral head mis-centering on eye lens dose and investigates discrepancies between measured and system-reported dose metrics using a low-cost pediatric head phantom.

MATERIALS AND

METHODS

A low-cost tissue-equivalent pediatric head phantom was constructed locally and validated using CT number comparisons with reference tissue values. Eye lens dose was measured using a pencil ionization chamber at the isocenter and at ±1-3 cm lateral displacements on two CT systems. Measured dose length product (DLP) values were compared with CT-reported DLP and air kerma-derived estimates. The data was analyzed statistically using Pearson correlation, paired sample t-tests, and one-way ANOVA.

RESULTS

Strong correlations were observed between isocenter and off-center doses (r = 0.994-0.998, p < 0.001). Although positional differences were not statistically significant (p > 0.05), a consistent asymmetric trend was observed, with higher doses on the right side. System-reported DLP substantially overestimated measured values (e.g., 720 vs. 304.83 mGy·cm).

CONCLUSION

Lateral mis-centering introduces systematic dose distribution asymmetry and significant discrepancies in CT dose reporting. These findings highlight the importance of accurate patient positioning and caution in interpreting system-reported dose metrics in pediatric imaging.