## 2 Materials and Methods
Because of the changes in ICRP 103, CT examinations can provide estimates of the effective dose, differing substantially with regard to the ICRP reports. According to the European Guidelines: the effective dose E\({}_{\text{d}}\) can be estimated from DLP values by:  
\[\text{Effective dose}\ (\text{E}_{\text{d}})=\text{DLP}\times\text{k} \tag{8}\]  
E\({}_{\text{d}}\) is measured in mSv, while k (in units of mSv/(mGycm)) is the coefficient factor taken from ICRP103 and is considered only for the regional anatomy scanned. This method of calculation underestimates the E\({}_{\text{d}}\) when the dose length product is estimated using the CTDIvol and scan range, because the length that is irradiated is usually more than the prescribed scan length [19, 20]. As a result, the newly developed CT scanners display DLP and contain the entire length that was irradiated, not only the length prescribed for the scan. In this study, we used the published coefficient factors in Table 2 to estimate the effective dose. The effective dose can be calculated using different Monte Carlo simulation software packages [23]. Two valuable data resources are the National Radiological Protection Board in the UK and the Institute of Radiation Protection in Germany [24; 25]. Monte Carlo simulation is considered to be the best complete computational method for the estimation of organ and tissue radiation doses in computed tomography. The simulations account for many scanner specifications such as beam collimation, filtration, scanner geometry, tube potential, and the CT dose parameters (CTDivol, DLP, scan length L) for a given CT exam. In this work, Monte Carlo simulation CT-Expo version 2.6, which is Microsoft Excel Spreadsheet-written in Visual Basic for the calculation of the patient dose in CT examinations, was used (Figure 1) [26]. CT-Expo v2.6 facilitates the calculation of the dose quantities such as weighted (CTDl\({}_{\text{w}}\)), volume (CTDl\({}_{\text{vol}}\)), size-specific dose estimate (SSDE), dose-length product (DLP), organ doses, and effective dose according to ICRP 60 and 103. Using CT-Expo v2.6, the dose calculations for all age groups and genders can be estimated in all existing scanner models. In CT-Expo v2.6, the 'Light' module, which offers a simplified calculation method with predefined standard CT examinations of standard-sized adults, was used. The calculation can be performed independently of the type of scanner in use and only requires the corresponding CTDl\({}_{\text{vol}}\) and DLP values. These are provided by most scanners. Hence, only the effective and organ doses remain to be assessed. Microsoft Excel 2010 was used to perform the effective dose calculations. The statistical analysis was performed using SPSS (Version 25, SPSS Inc., Chicago, IL, USA) and Microsoft Excel 2010. The data are presented as the mean \(\pm\) standard deviations. All the displayed protocol information regarding the radiation dose to the patient or dosimetry metrics (CTDlvol and DLP) is recorded. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Regional Anatomy**} & \multicolumn{3}{c}{**Dose Length Product to E\({}_{\text{d}}\) Conversion Factors (k)**} \\  & & **[mSv/(mGy \(\times\) cm)]** & & **Phantom** \\ \cline{2-5}  & **[PERSON]. et al. [21]** & **European Commission Guidelines [22]** & **European Commission NRPB-W67 (2005)** & **Module (cm)** \\ \hline Head & 0.0021 & 0.0023 & 0.0021 & 16 \\ Chest & 0.014 & 0.017 & 0.014 & 32 \\ Abdomen & 0.012 & 0.015 & 0.015 & 32 \\ Pelvis & 0.019 & 0.019 & 0.015 & 32 \\ \hline \hline \end{tabular} National Radiological Protection Board (NRPB). Dose-length product (DLP), \(E_{d}\) = k \(\times\) DLP.  
\end{table} 
Table 2: Reported DLP to E\({}_{\text{d}}\) conversion factors. Figure 1: CT-Expo scan range for adults; all organs doses HT are based on conversion coefficients for adult standard patients (AdAM, EVA).