N. A. Alomairy et al.: Radioprotection 2026, 61( 2), 132 – 139 135 Table 3. Correlation matrix between variables. Variables Age( y) KVp mAs CBT mm ESD( mGy) MGD( mGy)
Age( Year) |
Correlation P-Value |
1.00 |
�0.003 0.96 |
�0.11 0.01 |
0.06 0.34 |
�0.16 * 0.02 |
�0.17 ** 0.01 |
Tube voltage( kVp) |
Correlation |
�0.003 |
1.00 |
0.61 ** |
0.75 ** |
0.54 ** |
�0.03 |
|
P-Value |
0.96 |
|
<. 001 |
<. 001 |
<. 001 |
0.69 |
Tube current- time( mAs) |
Correlation |
�0.11 |
0.61 |
1.00 |
. 56 ** |
0.92 ** |
0.45 ** |
|
P-Value |
0.01 |
<. 001 |
|
<. 001 |
<. 001 |
<. 001 |
CBT( mm) |
Correlation |
0.06 |
0.75 ** |
0.56 ** |
1.00 |
0.30 ** |
�0.42 ** |
|
P-Value |
0.34 |
<. 001 |
<. 001 |
|
<. 001 |
<. 001 |
* Correlation is significant at the 0.05 level( 2-tailed). ** Correlation is significant at the 0.01 level( 2-tailed).
Table 4. Multiple linear regression analysis predicting mean glandular dose( MGD). Predictor variable Coefficient( B) Std. Error t-value p-value 95 % CI Significance
Constant |
0.0873 |
0.042 |
2.093 |
0.037 |
[ 0.005, 0.169 ] |
* |
Age( Y) |
0.0002 |
0.0003 |
0.696 |
0.487 |
[ �0.0003, 0.0007 ] |
ns |
CBT( cm) |
�0.0499 |
0.0034 |
�14.734 |
< 0.001 |
[ �0.057, �0.043 ] |
** |
kVp |
0.0054 |
0.0017 |
3.180 |
0.002 |
[ 0.002, 0.009 ] |
** |
mAs |
�0.0021 |
0.0004 |
�4.719 |
< 0.001 |
[ �0.003, �0.001 ] |
** |
ESD( mGy) |
0.4046 |
0.0177 |
22.843 |
< 0.001 |
[ 0.370, 0.439 ] |
** |
negatively associated with ESD( r = �0.16, p = 0.02) and MGD( r = �0.17, p = 0.01). Tube voltage( kVp) is positively related to tube current-time( mAs) by r = 0.61, p < 0.001, CBT by r = 0.745, p < 0.001, and ESD by r = 0.54, p < 0.001. However, there is no significant correlation with MGD. Tube current-time( mAs) also significantly correlates positively with CBT, r = 0.56, p < 0.001; ESD, r = 0.92, p < 0.001; and MGD, r = 0.45, p < 0.001. Finally, CBT shows a positive correlation with ESD( r = 0.30, p < 0.001) and a negative correlation with MGD( r = �0.42, p < 0.001).
Multiple linear regression was conducted to determine the independent predictors of MGD. As shown in Table 4, the model was significant( F( 5, 306) = 338.8, p < 0.001), explaining approximately 84.7 % of the variance in MGD( Adjusted R 2 = 0.844). Compressed breast thickness( CBT) was a strong negative predictor of MGD( B = �0.0499, p < 0.001), and tube voltage( kVp) and entrance skin dose( ESD) were positive predictors. Noticeably, mAs had a strong inverse correlation with MGD( B = �0.0021, p < 0.001). Age did not appear to be a predictor in this model.
3.3 Comparison with international studies
The comparison of the MGD and CBT values of the current study with those reported in previous studies, as shown in Table 5, shows significant differences in radiation dose and breast thickness among various populations. The mean CBT values in the current study( 39.70 mm for CC and 52.70 mm for MLO) are in the lower to mid-range, with Sudan and Iran having the highest CBT values. Similarly, the MGD values in this study( 0.32 mGy for CC and 0.36 mGy for MLO) are significantly lower than the values reported in international studies, in which the MGD values range from 1.21 to 2.40 mGy.
4 Discussion
4.1 Assessment of mean glandular dose( MGD) in mammography
The justification and optimization of the radiation dose to patients are the main principles of radiation protection. Since there is a lack of sufficient data for the breast and due to the possibility of giving a dose higher than the limit, the calculation of MGD for patients undergoing mammography is very important when considering optimization in dose delivery. In this study, the values of MGD obtained for MLO projections were higher than those for CC projections, which can be reasonably explained by the increased breast thickness in the MLO view. MLO projection includes the pectoralis muscle that is not so obviously included in the CC projection. Additional thickness and density of the breast tissue from the pectoralis muscle results in greater attenuation of the beams( Cheddad et al., 2014; Suliman et al., 2023). Attenuation happens in beams upon the absorption or scattering of an X-ray beam through the breast tissue it is passing through, decreasing the intensity of the radiation reaching the detector. Since more X-ray energy is needed to penetrate the thicker tissue in the MLO view, a higher MGD would result in adequately imaging the breast tissue, especially the deeper structures( Di Maria et al., 2022). It is possible to attribute several radiation exposure factors to this increase in MGD for the MLO