A clinically feasible model for size-specific estimation of eye lens dose in head CT

This study aimed to develop and validate a simplified, size-specific model for estimating eye lens dose during head CT imaging, addressing the limitations of generalized size-based methods for anatomically peripheral structures. An equation using effective diameter (D_Eff) was derived from Monte Carlo simulations covering head sizes of 9.9-19.5 cm and CTDI_vol values of 7-160 mGy. D_Eff was selected for its direct measurability from axial CT images. Validation was performed using OSL dosimeters in phantoms across three scanner platforms, comparing model estimates with measurements and SSDE values calculated by AAPM Reports 204 and 293.The equation was derived for 120 kV head CT protocols. The final exponential model demonstrated excellent agreement with reference values R² = 0.996, MAE = 0.94 mGy, RMSE = 1.27 mGy). SSDE-based estimates showed larger discrepancies, particularly in smaller head sizes. The model's correction factor exhibited a more gradual decline with increasing D_Eff, accurately reflecting the dose-size relationship of anteriorly located structures. This study presents a practical size-specific approach for eye lens dose estimation in head CT, providing better alignment with reference values than generalized SSDE methods. The model can be readily implemented in clinical workflows, particularly benefiting emergency scenarios requiring rapid individualized dose estimation.