Paediatric diagnostic reference levels in computed tomography: a systematic review

Abstract

This study aims to review the existing literature on diagnostic reference levels (DRLs) in paediatric computed tomography (CT) procedures and the methodologies for establishing them. A comprehensive literature search was done in the popular databases such as PubMed and Google Scholar under the key words ‘p(a)ediatric DRL’, ‘dose reference level’, ‘diagnostic reference level’ and ‘DRL’. Twenty-three articles originating from 15 countries were included. Differences were found in the methods used to establish paediatric CT DRLs across the world, including test subjects, reference phantom size, anatomical regions, modes of data collection and stratification techniques. The 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 dosimetric quantities chosen in the majority of publications. However, the size-specific dose estimate was a growing trend in the DRL concept of CT. A 16 cm diameter phantom was used by most of the publications when defining DRLs for head, chest and abdomen. The 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 DRL ranges for the head region were 18–68 mGy (CTDIvol) and 260–1608 mGy cm (DLP). 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 aged 0–18 years. The wide range of DRL distributions in chest and abdomen regions can be attributed to the use of two different reference phantom sizes (16 and 32 cm), failure to follow a common methodology and inadequate dose optimisation actions. Therefore, an internationally accepted protocol should be followed when establishing DRLs. Moreover, these DRL variations suggest the importance of establish a national DRL for each country considering advanced techniques and dose reduction methodologies.

Establishment of national diagnostic reference levels for computed tomography procedures in Sri Lanka: first nationwide dose survey

“…However, NC studies of chest and abdomen regions show a better optimisation than the head NC procedures. In addition, the DLP/CTDI vol ratio can be used to identify trends in scan lengths used [25]. Although the DRL based on CTDI vol is comparatively lower in NC chest and NC abdomen procedures, the DLP/CTDI vol ratios obtained were remarkably higher (47.3 and 68.6, respectively) compared with those in similar studies.…”

Dose reference level based on size-specific dose estimate (SSDE) and feasibility of deriving effective body diameter using tube current and time product (mAs) for adult chest and abdomen computed tomography (CT) procedures

“…The DRL is a widely accepted dose auditing tool that aids CT users in optimising the scan protocol by studying current practices. Therefore, establishing a DRL for a specific institution, local area, or country for the standard radiological procedures is of utmost importance [9]. Recently, in Sri Lanka, NDRL was established, which included nearly 40% of the total CT facilities in the country [17].…”

“…However, the dose matrices, CTDI vol and DLP can not be used to predict the actual dose received due to the changes in patient body size or composition because the CTDI vol is measured using a standard size tissue-equivalent phantom (usually of 16 cm and 32 cm diameter) which rarely mimic the size of the scanned body region [9]. The size-specific dose estimate (SSDE) provides better insight into the patient dose during CT imaging by taking into account both patient size and tissue composition.…”

Applying the AAPM 293 report to estimate the absorbed dose during head computed tomography: using head circumference for rapid dose estimation

“…Emerging evidence demonstrates a patient’s absorbed dose depends on the computed tomography (CT) scanner radiation dose output during CT examinations ( 1 - 3 ). The most common scanner output dose metrics for CT systems are the volumetric CT dose index (CTDI vol ) and dose-length product (DLP) ( 4 , 5 ). CTDI vol and DLP indicate the absorbed dose of polymethyl methacrylate (PMMA) phantoms with defined diameters of 16 and 32 cm for the head and body, respectively ( 6 - 9 ).…”