We retrospectively assigned sixty children that have underwent computed tomography (CT) examination between June 2014 and August 2018. We divided them into two groups (The 30 patients CT examination with conventional method from June 2014 to August 2016 and the 30 pediatric patients CT examination with new method from June 2016 to August 2018).
The conventional method for group A performed at 3 steps (1. Obtain the front scout view, 2. Obtain the side scout view, and 3. Main scan). The new method for group B performed at the 4 steps (1. Obtain the side scout view with table position correction, 2. Patient correction at the scan isocenter, 3. Obtain the front scout view, and 4. Main scan)(Figure, 1 and 2).
We used a 64-row CT scanner (LightSpeed VCT; GE Healthcare). Scan parameters were tube voltage: 80 kV, tube current: automatic tube current modulation used, noise index 16, slice thickness 5 mm, rotation time: 0.4 s / rot, and helical pitch: 1.375, reconstruction kernel:standard.
Measurement of the radiation dose and image noise
CTDIvol and DLP displayed on the CT console were recorded and we then compared both groups. A region of interest of 5-10 mm2 was set for the muscle tissue in the obtained simple CT image and the average value at 4 points was calculated. We compared the CTDIvol, DLP, and image quality of pediatric positioning at the CT examination in both groups. Figure.3
To compare the male-to-female ratio we used the chi-square test. For the comparison of height, weight, age, radiation dose, and SD of CT number under both groups, we used the Mann-Whitney U test. Values of p < 0.05 were considered to be statistically significant.
The pediatric patient characteristics show Table 1. There were no significant differences in the pediatric patient characteristics in both groups.
In Group A, median (minimum-maximum) values for CTDIvol, DLP and SD were 0.45 (0.3-0.9) mGy and 7.7 (4.4-13.7) mGy-cm, and 23.8 (18.3-37.5) HU, respectively. In Group B, median (minimum-maximum) values for CTDIvol, DLP and SD were 0.4 (0.3-0.6) mGy and 7.1 (4.2-13.8) mGy-cm, and 20.3 (11.3-28.8) HU, respectively. There were no significant differences in the CTDIvol and DLP between both groups (p=0.42, p=0.44), however, there were significant differences in the SD value in both groups (p <0.01)(Figure.4-6).