BACKGROUND: The rapid advancement of computed tomography (CT) has greatly improved clinical diagnosis but has also introduced new challenges in radiation protection. This study aimed to evaluate the relationship between organ doses from Monte Carlo (MC) simulations and CT dose metrics for head CT exams with organ dose modulation (ODM), and to develop a simplified method for estimating individual organ doses. METHODS: A CT source model including the X-ray energy spectrum, bowtie filter, fan beam shape, and rotational motion of the tube was constructed and validated. The modeling was divided into two different exposure regions based on the ODM technical principles: the 100° range on the anterior side of the skull (tube current reduction region) and the remaining 260° (tube current constant region). The source model was validated by comparing the error between the MC-simulated weighted CT dose index (CTDI RESULTS: Comparison results for CTDI CONCLUSIONS: There is a strong correlation between organ dose and organ-specific SSDE in ODM head CT examinations. However, activating the ODM results in significant differences in estimation coefficients for head CT exams with a fixed tube current, which provides a practical way to determine organ doses for individual patients undergoing head CT scans.