K. Mitsui et al.: Radioprotection 2025, 60( 1), 37 – 43 39
Fig. 1. Relationships of CTDIvol against ED( a) and WED( b). The solid lines represent regression lines. Fig. 2. Relationships of SSDE against ED( a) and WED( b). The solid lines represent regression lines.
The SSDE also showed positive linear correlations with the ED and WED( Fig. 2, p < 0.001 for both). The correlation between the SSDE and WED was higher than that between the SSDE and ED( p = 0.006). When correlations with the ED and WED were compared between the CTDIvol and SSDE, the correlation coefficients were lower( p < 0.001 for both), and the slopes of the regression lines were smaller( p < 0.001 for both) for the SSDE.
Although the DLP showed positive correlations with the ED and WED( Fig. 3, p < 0.001 for both), the correlation was lower for the DLP than for the CTDIvol and SSDE( p < 0.001 for all). The plots of the DLP against the WED appeared to be divided into two groups: high-DLP and low-DLP groups. The DLP at a given WED was higher in the high-DLP group than in the low-DLP group.
The CTDIvol and SSDE showed significant positive correlations with body weight( Fig. 4, p < 0.001 for both), body height( Fig. 5, p < 0.001 for both) and BMI( Fig. 6, p < 0.001 for both). Although the correlation coefficients were highest for weight among the body size indices, they were definitely lower for weight than for the ED( p < 0.001 for both).
4 Discussion
The CTDIvol showed high positive linear correlations with the ED and WED, indicating that the AEC used in this study modulated the radiation dose in a manner that closely reflected X-ray attenuation by the head. Whereas the ED is a simple index of cross-sectional size, the WED is calculated considering differences in attenuation among tissues. The correlation with the CTDIvol was higher for the WED than the ED, further suggesting successful dose modulation by AEC according to the attenuation strength. For radiation dose management, evaluating the relationship between the CTDIvol and the ED or WED appears to be helpful. From this relationship, a typical dose at the facility for any ED or WED can be determined. During daily dose management, it is recommended to plot the CTDIvol against the ED or WED and identify outliers to be investigated.
The CTDIvol represents CT scanner output rather than the absorbed dose to the patient. When the head is larger than the 16-cm dosimetry phantom, the absorbed dose to the patient is lower than in the CTDIvol because of increased attenuation in