Evaluation of Size-Specific Dose Estimates for Optimizing Pediatric Chest CT Protocol

The importance of estimating patient-sized adjusted radiation dose for pediatric computed tomography (CT) has long been accepted. High doses of ionizing radiation to children are often common in chest CT examinations, as the volume CT dose index (CTDIvol) is measured by a 32 cm phantom. Our study aimed to evaluate the effectiveness of size-specific dose estimate (SSDE) to compensate for the underestimated pediatric absorbed dose.       CTDIvol and dose-length product (DLP) of 320 pediatric chest CT (<1, 1-5, 5-10, 10-15 years) were obtained from Picture-Archiving and Communication System (PACS) in a hospital affiliated with the Shiraz University of Medical Sciences. CTDIvol was converted to SSDE based on the patient's effective diameter. The Statistical Package for Social Science (SPSS) was used for data analysis.    The variations between standard phantom (32cm) and the patients' mean effective diameter were approximately 65%, 57%, 47%, and 38%, across   <1, 1-5, 5-10, 10-15 year age groups, respectively.  The mean of SSDE for each age group was significantly higher than the corresponding CTDIvol values. Also, mean CTDIvol and SSDE values differed between age groups significantly (p<0.001). Results showed a strong correlation between age and the two-dose indicators, CTDIvol (0.361) and SSDE (0.184), with p<0.05.  Pediatrics receive radiation doses comparable to the dose for adult-sized patients in chest CT protocol if the dosimetry procedure is not individualized. Thus, applying a size-based conversion coefficient is paramount in estimating the absorbed dose in pediatric chest CT.