## 3 Results
### Patient Radiation Dose Determination
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline \multirow{2}{*}{**Age Group**} & **CTDI\({}_{\text{vol}}\)** & **DLP** & **SSDE\({}_{\text{Dw}}\)** & \multirow{2}{*}{**Organ Dose (mGy)**} \\  & **(mGy)** & **(mGy. cm)** & & **(mGy)** \\ \cline{3-5}  & & & & **Brain** & **Eye Lens** \\ \hline \multicolumn{5}{c}{**Median (IQR)**} \\ \hline
0 to 6 months & 14.1 \({}^{\star}\) & 210.4 (201, 216.7) & 15.4 (14.8, 15.8) & 21 (21, 21) & 24 (23.9, 24.1) \\
6 months to 3 years & 21.1 \({}^{\star}\) & 350.4 (337.8, 363.1) & 20.1 (19.6, 20.6) & 26.2 (26.2, 26.3) & 32.9 (32.9, 32.9) \\
3 to 6 years & 27.4 \({}^{\star}\) & 482.8 (460.8, 504.7) & 25.3 (24.6, 25.7) & 28.4 (28.4, 28.5) & 35.6 (35.6, 35.6) \\
6 to 12 years & 31.4 \({}^{\star}\) & 567.6 (551.9, 577) & 28.1 (27.3, 28.8) & 33 (32.9, 34.8) & 39.6 (39.6, 40.4) \\
12 to 15 years & 40.1 (40.1, 41.2) & 752.6 (721.2, 786.3) & 35.1 (34.6, 36) & 39.5 (39.4, 41.2) & 50.1 (49.9, 52) \\ \hline \multicolumn{5}{c}{CTDI\({}_{\text{vol}}\), volumetric CT dose index; DLP, dose length product; SSDE\({}_{\text{Dw}}\), size-specific dose estimate based on the water-equivalent diameter. \({}^{\star}\) The CTDI\({}_{\text{vol}}\) remains constant across the age ranges.} \\ \end{tabular}
\end{table} 
Table 2: Patient radiation dose categorized into five age groups for computed tomography head examinations. than that for the 3-to-6-year age group. However, the median value for the 6-to-12-year age group was lower than that for the 6-month-to-3-year and 3-to-6-year age groups. The 12-to-15-year age group exhibited the highest median value of the mean CT number within the ROI. Table 3 presents the model and evaluation metrics derived from both the univariate and multivariate linear regression analyses. The univariate analysis indicated a significantly high R-squared value (0.87) for the SSDEDw with age and a moderately R-squared value (0.63) with weight. Both models demonstrated statistical significance (\(p<0.001\)). Multivariate linear regression analysis revealed that the model of the SSDEDw with age and weight exhibited a relatively high R-squared value of 0.87, which was significant (\(p<0.001\)) and had a low residual standard error (RSE). The model was derived from the univariate linear regression of the Dw with age and weight and showed R-squared values of 0.50 and 0.47, respectively, which were significant  
Figure 2: Box plot of the mean CT number in the region of interest (ROI) (HU) across the five age groups. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{ \begin{tabular}{c} **Variable** \\ **Dependent** **Independent** \\ \end{tabular}  } & \multicolumn{3}{c}{ \begin{tabular}{c} **Univariate Linear Regression** \\ **Model** \\ \end{tabular}  } & \multicolumn{3}{c}{ \begin{tabular}{c} **Multivariate Linear Regression** \\ **Evaluation Metrics** \\ \end{tabular}  } & \multicolumn{3}{c}{\ \begin{tabular}{c} **Linear Regression** \\ **Evaluation Metrics** \\ \end{tabular}  } \\ \hline \multirow{4}{*}{
\begin{tabular}{c} **SVM**  
(\(p<0.001\)). The multivariate linear regression analysis of the Dw with age and weight yielded a moderate R-squared value of 0.52, which was significant (\(p<0.001\)) and had a low RSE. Figure 3 shows a scatterplot of the association between age and Dw, with the trend highlighted by a locally weighted scatterplot smoothing (LOWESS) curve shown as a red line. Noticeably, the Dw value was the lowest during early infancy and increased with age.