Correlation analysis of organ doses determined by Monte Carlo simulation with dose metrics for patients undergoing chest-abdomen-pelvis CT examinations

ObjectivesThis study aimed to determine organ doses based on Monte Carlo (MC) simulations for individual patients undergoing routine adult chest abdomen-pelvis computed tomography (CT) examinations and to evaluate the correlations of organ doses with patient size and dose metrics.MethodsMC simulations were performed by reading detailed descriptions of the CT scanner, scanning parameters, and CT images of phantoms and patients into the simulation software. The simulation models were validated by comparing the simulated doses with the doses measured by in-phantom dosimetry using radiophotoluminescent glass dosimeters and an adult anthropomorphic phantom, and organ doses for 80 patients were determined from the simulation results. To obtain patient size and dose metrics, body mass index and volume computed tomography dose index (CTDIvol) data were collected. Water equivalent diameter (WED) was calculated from the CT images of each patient. Size-specific dose estimates (SSDE) were calculated using CTDIvol and average WED over the scan range, and organ specific SSDE were calculated using the average CTDIvol and WED over each organ position. The correlations of organ doses with dose metrics were evaluated using coefficients of determination.ResultsOrgan doses increased with patient size, and the doses for obese were approximately two to three times higher than those for underweight patients. Organ doses exhibited stronger linear relationships with organ specific SSDE (R² ≥ 0.82) than other dose metrics.ConclusionsThe linear regression fits between organ doses determined by MC simulation and organ-specific SSDE are valuable for simplified and accurate organ dose estimation for individual patients undergoing CT examinations.