Evaluation of Impact of Factors Affecting CT Radiation Dose for Optimizing Patient Dose Levels

The dose metrics and factors influencing radiation exposure for patients undergoing head, chest, and abdominal computed tomography (CT) scans were investigated for optimization of patient dose levels. The local diagnostic reference levels (DRLs) of adult CT scans performed in our hospital were established based on 28,147 consecutive examinations, including 5510 head scans, 9091 chest scans, and 13,526 abdominal scans. Among the six CT scanners used in our hospital, four of them are 64-slice multi-detector CT units (MDCT(64)), and the other two have detector slices higher than 64 (MDCT(H)). Multivariate analysis was conducted to evaluate the effects of body size, kVp, mAs, and pitch on volume CT dose index (CTDI(vol)). The local DRLs expressed in terms of the 75th percentile of CTDI(vol) for the head, chest, and abdominal scans performed on MDCT(64) were 59.32, 9.24, and 10.64 mGy, respectively. The corresponding results for MDCT(H) were 57.90, 7.67, and 9.86 mGy. In regard to multivariate analysis, CTDI(vol) showed various dependence on the predictors investigated in this study. All regression relationships have coefficient of determination (R(2)) larger than 0.75, indicating a good fit to the data. Overall, the research results obtained through our workflow could facilitate the modification of CT imaging procedures once the local DRLs are unusually high compared to the national DRLs.