Improved organ absorbed dose estimation in abdominal CT using DICOM header-based tube current modulation profiles: Validation with measurements and Monte Carlo simulations.

PURPOSE: Precise determination of organ absorbed doses in computed tomography (CT) is vital for evaluating radiation risk and optimizing radiation dose. This study aimed to improve the accuracy of organ absorbed dose estimates in abdominal CT by integrating tube current modulation (TCM) profiles-extracted from the Digital Imaging and Communications in Medicine (DICOM) headers-into Monte Carlo (MC) simulations. The proposed study was validated by comparing the simulation results with direct measurements.

METHODS

The Particle and Heavy Ion Transport code System (PHITS), an MC simulation model, was validated by comparing its simulated weighted CT dose index (CTDIw) with measurements obtained using a 32-cm PMMA phantom on a 256-slice multidetector CT scanner. Organ doses were measured using radiophotoluminescence glass dosimeters placed at the anatomical locations of various organs within an abdominal phantom. Scans were performed under both fixed tube current conditions and TCM with noise indices (NI) of 9 and 11. A voxel-based phantom model was constructed from CT image data, and TCM profiles were extracted from DICOM headers for use in the simulations.

RESULTS

The simulated CTDIw values were within 10% of the measured data. The relative differences between simulated and measured organ absorbed doses for the liver, gallbladder, stomach, spleen, kidneys, and pancreas ranged from -14.0% to 7.87% across both fixed tube current and TCM protocols. Slightly larger deviations were noted for the kidneys under TCM at NI 9. While the average dose differed depending on the NI setting, the dose distribution trend under TCM was comparable to that of fixed tube current scans.

CONCLUSION

The agreement between simulated and measured organ doses, including CTDIw, was consistent across all protocols. The observed consistency in dose distribution patterns affirms the reliability and applicability of the proposed correction method for accurate and protocol-specific organ dose estimation in abdominal CT.