Electronic ISSN 2287-0237
The use of CT scanning in pediatric patients has been increasing since the introduction of multidetector-computed tomography (MDCT), resulting in high radiation dose to pediatric patients. As the cells in children have a more rapid growth than in adults and they have a longer living time left, the risk of cancer in long-term from radiation exposure should be more of a concern.1 Children who receive radiation in early life are at risk for cancer and this risk will last for a lifetime.3 Due to this concern, The International Commission on Radiological Protection (ICRP) defined the guidelines and recommendations about the diagnostic reference levels (DRLs) for pediatric patients in ICRP Publication 121. However, DRLs may vary upon the race or physical appearance of the population studied.4 Thus, the appropriate DRLs should be categorized by age and part of the body to scan (age-based DRL for pediatric CT) using the data from the national survey of United Kingdom in 2003 which was published in 2005 and the national survey of Switzerland in 2005 which was published in 2008.5,6
There has been no published national survey of DRLs in Thailand, but there was a pilot study by Kritsaneepaiboon S, et al7 in 2001 which was published in 2012. It was a study by 3 medical schools that found the overall radiation dose in pediatric patients receiving CT scan of chest and abdomen was not as high as compared with those reported in United Kingdom and Switzerland. However, the dose was still varied among hospitals.7
According to our institute information collection in 2013, there was data of radiation dose in pediatric patients aged 8
Thus, this study was aimed to study the radiation dose in pediatric patients undergoing CT scan in our hospital after using this protocol in all CT scan abdomen studies.
This study was a prospective and descriptive study. The research proposal has been approved by Institutional Review Board, Royal Thai Army Medical Department before performing the study. The study target population were all patients aged 4
Data collected was the dose-length product (DLP) for 32-cm phantom size which was shown on the monitor in dose information zone. After getting the DLP, it was multiplied by 2 to be an adjusted DLP in order to be able to compare with the other studies that usually reported DLP for 16-cm phantom size. All consecutive cases that had performed CT scan of abdomen during the study period were included. For all CT studies obtained in this study, the images were acquired using a 64 slice Toshiba Aquillion Prime scanner. The images were acquired at 1 mm thick slices and reconstructed to both 3 mm thick slices in axial, sagittal, and coronal planes for viewing. CT scan of abdomen of pediatric patients was routinely performed in 1 phase. No sample size calculation was done.
Statistical analysis
Data was described using descriptive statistics as mean, minimum value, maximum value and the 75th percentile of DLP. All data was categorized according to age group as th percentile collected from CT scan of abdomen before and after using protocol were compared using independent T-test. P value of ≤ 0.05 was considered significant.
During the study period, a total of 29 children were included in analysis, 13 were male and 16 were female. Among these patients, the third quartile of DLP (75th percentile) was 125.0, 228.0, 305.6 and 381.0 mGy.cm for the patients <1, 1 to <5, 5 to
As compared with the historical control group in our hospital before using the protocol, the mean DLP was significantly decreased in the group of
In an attempt to compare the DLP of our study with the previously reported in Thailand and Switzerland, the distribution of dose at the 75th percentile for each age group is shown in Table 2 and Chart 2.
An example of CT scan image of pediatric patients before and after using the new protocol is shown in the Figure3.
Table 1: Distribution of patient number, gender, mean values, range and 75th percentile of abdominal CT- DLP in each patient group
Figure 1: The DLP value at 75th percentile (third quartile) in mGy.cm for the patients in this study (New PMK) comparing to the historical control.
Table 2: The DLP value at the 75th percentile of our study as compared with the data previously reported.
Figure 1: The DLP value at the 75th percentile
Figure 3: Images of the pediatric patients performed CT scan of abdomen before (3A) and after (3B) using the new protocol.
In an attempt to reduce radiation dose to our pediatric patients, the new pediatric abdominal CT scanning protocol has been used in our hospital since 2016. In this new protocol, apart from the radiation dose reduction, indication of CT scan must be reviewed before making a schedule for CT. Moreover, CT scan was selected to be performed only in some phases, not routinely performed in all phases like a protocol for adult patients. Some parameters, for example, tube current (mA) and tube voltage (kVp) were also adjusted based on the patient’s body weight and length of the scan. As shown above, the DLP values at the 75th percentile were significantly lowered in the patient < 1 year-old, 1 to
However, there were some limitations in our study. First, a small number of patients was included and this may have resulted in a failure to detect the difference in some age groups. Second, the data about the quality of the image (both first and follow-up study) was not recorded. In an attempt to lower radiation dose delivered to the patients, the quality of the image is still important and needs to be evaluated too. Finally, the study period was short and the data about the clinical outcome was lacking. By including a higher number of patients and a longer follow-up time, it may be helpful for data collection in future studies.
The radiation dose that our pediatric patients received from undergoing CT scan of abdomen was acceptable after using the new protocol. However, more data collection in the future studies with more patients and longer period may lead to more helpful information. This may help answer whether lower doses of radiation are correlated with better clinical outcomes, such as lower incidence of malignancy from radiation.
