# Assessment of a Patient Dose Monitoring System for Average
## 4 Discussion  
The average glandular dose (AGD) collected by DoseWatch for a large number of images provided by two Selenia Dimensions mammography systems was assessed by calculating it independently using the Dance and Boone models. Additionally, the glandularity estimate based on actual breast density, rather than age and breast thickness as suggested by [PERSON] et al. [2], was verified for the two subgroups of patients in the study. The AGD evaluation method based on glandularity obtained through LIBRA software can be considered an independent method of dose calculation, as it uses the actual glandularity extracted from the acquired radiological images of the patients. As expected, the agreement between the mean AGD displayed by the two mammography units and the calculated AGD improved when the glandularity assessed by LIBRA was used (Table 5). Using the Dance method, comparable values were obtained with no statistically significant differences (row 2 of Table 5). However, when the Boone method was used to calculate the AGD, differences between the calculated AGD values and those provided by the mammography units remained statistically significant, even when using glandularity estimated from the DICOM images through LIBRA (row 4 of Table 5). This is particularly relevant, since Hologic units use the Dance model for AGD calculation. The present study also included [PERSON]'s method for comparison to ensure that the dose values obtained were below those provided by DoseWatch as a precaution. On average, for all the examinations considered, the displayed and calculated AGD values exceeding the maximum acceptable dose levels (according to guidelines) were 1.7% and 1.0%, respectively, while those exceeding the maximum achievable dose levels were 17.6% and 13.2%, respectively (Table 3 and Figure 2). Some procedures exceeded acceptable AGD levels due to potential inaccuracies in the thickness indicator, which could lead to an over- or underestimation of breast thickness. This in turn could affect tube voltage, exposure, and the anode-filter combination, typically resulting in a higher AGD. \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{\(p\)-Value} \\ \cline{2-3}  & **Dim1** & **Dim2** \\  & **(519 Images)** & **(532 Images)** \\ \hline AGD Dance vs. AGD DoseWatch & 0.007 & 0.017 \\ AGD Dance-LIBRA vs. AGD DoseWatch & 0.695 & 1.000 \\ AGD Boone vs. AGD DoseWatch & \textless{}0.001 & \textless{}0.001 \\ AGD Boone-LIBRA vs. AGD DoseWatch & 0.017 & 0.004 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Two-tailed paired \(t\)-test (0.05 level of significance) to study the differences between displayed dose values (DoseWatch) and AGD calculated using Dance’s and Boone’s methods with different glandularity estimates for the two subgroups of patients. The close match between the displayed and calculated AGD values for the selected patient subgroup is understandable, as their age, kV, HVL, and CBT values fell within the range of the tabulated values for the c and g coefficients (Table 1) according to the Dance model. As a good approximation, the independent AGD calculation method using the Dance model and tabulated glandularity is reliable (as confirmed by the small effect size found) and simplifies the process by eliminating the need for individual image analysis using LIBRA. As widely demonstrated, AGD significantly depends on the estimation of breast glandularity [36]. Standardized dose calculation models commonly used to estimate AGD require careful interpretation to account for the uncertainties they may be subject to [23; 28; 29; 30]. Inaccurate mammographic breast composition estimates can lead to incorrect dose assessments and an inaccurate evaluation of the cancer risk associated with radiation exposure in mammography [9; 10; 11; 12; 36; 37]. This issue is more critical given that glandular tissue distribution inside the breast is not uniform, but heterogeneous, which can significantly influence the dose coefficients calculated through Monte Carlo simulations [38].