# Assessment of Imaging Protocol and Patients Radiation Exposure in Computed Tomography Colonography
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Mode**} & \multirow{2}{*}{**Tube Voltage (kVp)**} & \multicolumn{2}{c}{**(A)**} & \multirow{2}{*}{**Rotation Time (s)**} & \multirow{2}{*}{**Pitch**} & \multirow{2}{*}{
\begin{tabular}{c} **Slice Thickness** \\ **(mm)** \\ \end{tabular} } \\ \cline{3-3} \cline{5-6}  & & & **Supine** & & & **Prone** \\ \hline Auto mA & \multirow{2}{*}{120} & 287.5 \(\pm\) 17 & 287.5 \(\pm\) 17 & 0.85 \(\pm\) 0.02 & \multirow{2}{*}{0.9 *} & \multirow{2}{*}{0.67 *} \\ (Philips) & & (275–300) & (275–300) & (0.84–0.87) & & \\ \hline Auto mA (GE) & \multirow{2}{*}{116.6 \(\pm\) 8.1} & 241.6 \(\pm\) 70 & 245.8 \(\pm\) 65.9 & \multirow{2}{*}{0.5 \(\pm\) 0.1 (0.4–0.7)} & 1.1 \(\pm\) 0.2 & \multirow{2}{*}{0.62 *} \\ (100–120) & & (150–325) & (150–325) & & & \\ \hline Manual mA & \multirow{2}{*}{120} & 212.3 \(\pm\) 104 & 213.2 \(\pm\) 105.5 & 0.52 \(\pm\) 0.06 & 1.32 \(\pm\) 0.1 & \multirow{2}{*}{0.62 *} \\ (GE) & & (100–450) & (100–450) & (0.5–0.7) & (0.98–1.37) & \\ \hline \hline \multicolumn{6}{c}{**(B)**} \\ \hline \hline \multirow{2}{*}{**Mode**} & \multicolumn{2}{c}{**CTDI\({}_{\text{vol}}\) (mGy)**} & \multirow{2}{*}{**DLP (mGy.cm)**} & \multirow{2}{*}{**Effective Dose (mSv)**} \\ \cline{2-2} \cline{4-4}  & **Supine** & & & **Prone** \\ \hline Auto mA & \multirow{2}{*}{16.2 \(\pm\) 2.9} & 14.6 \(\pm\) 2.6 & \multirow{2}{*}{1702.8 \(\pm\) 436.7 (1394–2011.6)} & \multirow{2}{*}{25.5 \(\pm\) 6.5 (20.9–30.1)} \\ (Philips) & & (14.2–18.3) & & & \\ \hline Auto mA (GE) & \multirow{2}{*}{9.6 \(\pm\) 4.8 (2.2–14.5)} & 9.1 \(\pm\) 4.6 & \multirow{2}{*}{1098.1 \(\pm\) 686.5 (204–2128.8)} & \multirow{2}{*}{16.4 \(\pm\) 10.2 (3.06–31.9)} \\ (GE) & & (2.8–19.7) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: (**A**): Mean \(\pm\) standard deviation (minimum \(-\) maximum) of the image acquisition parameter and radiation dose values according to the manufacturer and the tube current mode. * fixed values. (**B**): Mean \(\pm\) standard deviation (minimum \(-\) maximum) radiation dose values according to the manufacturer and the tube current mode. indication. In fact, after accounting for patient weight and body mass index, a profound--and unacceptable--variation in these measures remained. Most of the dose variation is due to variation in the adoption of multiphase protocols, larger scanning regions, or higher dose settings without awareness of the resulting dose burden these choices create. Thus, without considering patient weight, we can greatly improve the way of conducting CT simply by assessing CTDI\({}_{\text{vol}}\) and DLP. Figure 1B: The relation between the CTDI\({}_{\text{vol}}\) (mGy) and the DLP (mGy.cm), wide variation in DLP value as CTDI\({}_{\text{vol}}\) increases. (According to AAPM the CTDI\({}_{\text{vol}}\) (mGy) value according to the patient weight is 2-4 mGy for (50-70 kg), 3-6 mGy for (70-90 kg) and 5-9 mGy for (90-120 kg) [31]. In seeking to optimize patient dose consistent with sufficient image quality and with DLP depending proportionally on scan length, precise selection of scan length is important. Figure 2 illustrates the patient-effective dose (mSv) and CTDI\({}_{\text{vol}}\) (mGy) using the same parameter factors for patients in the supine position. The steps for the first three patients were found to provide optimum anatomical coverage while conversely the anatomical range situation for the last patients four and five was less favorable, the latter registering greater effective doses due to an associated need for wider variation in exposure parameters. As expected, compared to those of average body mass index (BMI, kg/m\({}^{2}\)) of 18-24.9, patient doses are greater for obese patients [32]. Figure 3A,B, show for two patients with the same scan parameters a 16.5% difference in effective doses, a matter arising from anatomical coverage, the yellow line indicating scan coverage, the green line delineating the upper part of the colon, and the red line the lower level.