Pediatric diagnostic reference levels in computed tomography: a systematic review.

This study aims to review the existing literature on Diagnostic Reference Levels (DRLs) in pediatric Computed Tomography (CT) procedures and methodologies for establishing them. A comprehensive literature search was done in the popular databases such as PubMed and Google Scholar under the key words "pediatric DRL", "dose reference level", "diagnostic reference level", and "DRL". 23 articles originated from 15 countries were included. Differences were found in methods used to establish the pediatric CT DRLs across the world including test subjects, reference phantom size, anatomical regions, modes of data collection and stratification techniques. Majority of the studies were based on retrospective patient surveys. The head, chest and abdomen were the common regions. The Volume Computed Tomography Dose Index (CTDIvol)and Dose Length Product (DLP) were the choice of dosimetric quantities among majority of publications. However, the Size Specific Dose Estimate (SSDE) was a growing trend in the DRL concept of CT. The 16 cm diameter phantom was used by most of the publications when defining DRLs for head, chest and abdomen. Majority of the DRLs were given based on patient age and the common age categories for head, chest and abdomen regions were 0-1, 1-5, 5-10 and 10-15 years. The DRLs for head region were ranging from 18-68 mGy and 260-1608 mGy.cm. For chest and abdomen regions the variations were 1.0-15.6 mGy, 10-496 mGy.cm and 1.8-23 mGy, 65-807 mGy.cm respectively. All these DRLs were established for children of 0-18 years. The wide range of DRL distribution in chest and abdomen region can be attributed to using two different reference phantom sizes (16 cm and 32 cm), failure to follow a common methodology and inadequate dose optimization actions. Therefore, an internationally accepted protocol should be followed when establishing DRL. Moreover, these DRL variations suggest the importance to establish a country's own NDRL considering advanced techniques and dose reduction methodologies.