Fig. 2 shown the regression analysis results between the BMI and dose.
In the chest Xp (left),
the correlation between BMI and dose [mAs] has the slope value of 0.250,
intercept of −2.307,
and correlation coefficient of R = 0.771 (p < 0.01).
In the CT examination (right),
the correlation between BMI and CTDIvol has the slope value of 0.275,
intercept of −3.053,
and correlation coefficient of R = 0.815 (p < 0.01),
both of which showed a strong positive correlation.
Fig. 3 shown the regression analysis results between the dose [mAs] of Xp and CTDIvol,
with slope value of 0.859,
intercept of 0.636,
and correlation coefficient of R = 0.894 (p < 0.01),
showing a higher positive correlation than those between the BMI and dose.
Fig. 4 shown the regression analysis results between SSDE(Calc.,
CT) and SSDE(Est.,
Xp),
with slope value of 1.021,
intercept of 0.386,
and correlation coefficient of R = 0.767 (p < 0.01).
In both chest Xp and CT examination,
the correlation coefficient between the BMI and dose exceeded 0.7,
which was a strong positive correlation (Fig. 2).
The results displayed that the AEC system properly controls the dose according to the patient’s body size.
Based on this correlation result,
a certain level of dose estimation can be obtained using the BMI before examination.
The correlation between the dose [mAs] of Xp and CTDIvol was 0.894,
which was strongly correlated (Fig. 3).
If other dose data were obtained in advance,
the dose can be estimated with higher accuracy compared to the estimation from BMI.
SSDE(Calc.,
CT) and SSDE(Est.,
Xp) were quasi-equivalent (p < 0.01) (Fig. 4).
Fig. 3 and Fig. 4 suggest that CT dose can be estimated from Xp.
In the regression analysis between SSDE(Calc.,
CT) and SSDE(Est.,
Xp),
the ideal result is slope value of 1,
intercept of 0.
In this study,
the slope value of 1.021,
intercept of 0.386 (Fig. 4).
The cause is the propagation of errors during CTDIvol(Est.,
Xp) estimation.
Furthermore,
to calculate the CF(Est.,
Xp),
the patient’s body size was estimated largely due to the influence of image enlargement because the body thickness measurement was performed using chest Xp.
In chest Xp using the AEC system,
dose data cannot be obtained before examination.
In the CT examination,
the estimated CTDIvol and SSDE values are displayed after scout imaging,
and the actual dose data is obtained after imaging.
In this sutudy based on the output data analysis of the device,
the reliable dose estimation was possible without requiring simulation software,
making the provision of dosage information to patients before examination as well as risk communication useful.
Because the Definitions/units of indicators for each examination are different,
simple comparison is difficult.
Based on the analysis using the same patient's other examination data,
it is expected that a new dose index common to each modality will be defined in the future.