# Monitoring Pediatric Head CT Scan Dose Levels:
## 2 Materials and Methods  
The current study has been approved by the Health Service Company (SEHA), the research committee of Abu Dhabi, UAE, with the approval reference number SEHA-IRB-022 dated 27 April 2021. The SEHA is the official institution that owns and operates public hospitals and clinics within the Emirate of Abu Dhabi, the largest province in the United Arab Emirates (UAE) [14]. In addition, the Federal Authority for Nuclear Regulation (FANR) performs periodic checks on the readings of all CT systems within the country [15].  
Data on pediatric cases from January 2020 to December 2020 were obtained from the Sheikh Shakboot Medical City (SSMC), the largest hospital in the region, which is operated by the Mayo Clinic. The SSMC includes 732 medical beds [14]. The data were extracted from the Picture Archiving Communication System (PACS). SEHA's PACS system specialists pulled 250 pediatric head CT scans at random. The files included patient protocol files and dose reports related to each head CT scan procedure. In addition to the date of the CT scan and the type of CT machine, the protocol files and dose reports contain information regarding the patient's age, the tube voltage, tube current-time product, computed tomography dose index volume (CTDIvol), and dose-length product (DLP). The CTDIvol for head CT examinations was based on a 16 cm diameter phantom. The DLP is calculated by multiplying the CTDIvol by the length of the scanned volume and is reported in units of milligray centimeters (mGy-cm). Patient consent requirements are waived for retrospective data collection. All the collected medical image files were processed and preserved in the DICOM format using MicroDicom viewer software. A Python code was written to extract the required data from the 250 DICOM files. Data subjects were excluded if they had multiple exams elsewhere in the body or insufficient data from dose reports. The retrieved data were stored in a Microsoft Excel spreadsheet and divided into 4 groups based on their ages: Group 1 (children \(\leq\) 1 year of age), Group 2 (children \(>\) 1 year to \(\leq\)5 years), Group 3 (children \(>\) 5 years \(\leq\)10 years), and Group 4 (patients \(>\) 10 years \(\leq\)16 years).  
CTDIvol and DLP data were analyzed according to the minimum and maximum values, and the difference between them (i.e., the range). To ensure the accuracy of the analysis, a number of outlier data points were identified and excluded. Specifically, data points with very low values were excluded to ensure the robustness of the analysis. Furthermore, the values of the 1 st quartile (25 th percentile), 2 nd quartile (median, 50 th percentile), and 3 rd quartile (75 th percentile) were calculated. Finally, the 75 th percentile was used to make a comparison with the established DRLs from other published studies. In order to find relevant original research studies, a thorough search of the literature was performed on Web of Science, Scopus Medline, ProQuest Health, Medical Complete, PubMed, and ScienceDirect to find pediatric CT studies that have established DRLs. The search terms used were \"diagnostic reference levels\", \"pediatrics\", \"computed tomography\", \"CT\", and \"radiation dose\". The search was restricted to research articles published in the English language between 2015 and 2020. We intentionally focused on the most recent years' articles in order to have access to the most recently established DRLs. Articles were excluded if they (i) were conference abstracts, (ii) did not propose a pediatric DRL for computed tomography, and (iii) were phantom studies.