# Pediatric Local Diagnostic Reference Levels for CT Examinations: A Study Based on the European Guidelines on Diagnostic Reference Levels for Pediatric Imaging

## TL;DR

This study establishes local diagnostic reference levels for CT scans in children based on European guidelines, aiming to optimize radiation doses.

## Contribution

The study introduces pediatric local diagnostic reference levels (LDRLs) for CT exams in a large hospital, following updated European protocols.

## Key findings

- LDRLs for head, chest, and AP CT exams ranged from 15-65 mGy (CTDIvol) and 211-787 mGy·cm (DLP).
- Proposed LDRLs are lower than European DRLs except for older children and heavier patients.
- Weight-based protocols for body CT reduced radiation doses compared to age-based ones.

## Abstract

Background: Diagnostic reference levels (DRLs) are valuable tools for computed tomography (CT) dose optimization. The current study aimed to establish local DRLs (LDRLs) in pediatric patients who underwent head, chest, and abdomen-pelvis (AP) CT examinations after implementing age- and weight-based protocols according to the European Guidelines on Diagnostic Reference Levels for Pediatric Imaging.

Methods: The study included a total of 357 pediatric patients in a 16-slice CT unit at the nation's largest pediatric hospital who underwent head, chest, and AP CT examinations within a six-month period, from winter 2023 to spring 2024. The CT protocols were categorized based on age for head CT examinations and weight for body CT examinations. Patients’ demographic characteristics and exposure parameters were recorded. In addition to age and body weight, no contour, anteroposterior, or lateral dimensions were taken into account. We were unable to automatically incorporate size-specific dose estimation (SSDE) into our research because our device did not supply it. DRLs were calculated based on the third quartile of the distribution (75th percentile) of volume CT dose index (CTDIvol) and dose length product (DLP).

Results: LDRLs in terms of CTDIvol for head, chest, and AP CT examinations ranged from 15 to 65 mGy, 1 to 5 mGy, and 1 to 7 mGy, respectively. In terms of DLP per single acquisition, LDRLs for head, chest, and AP CT examinations varied from 211 to 787 mGy·cm, 18 to 226 mGy·cm, and 36 to 438 mGy·cm for the various patient groups, respectively. The proposed pediatric DRLs are lower than the European DRLs (EDRLs) except for patients above six years old in head CT examinations and the 50-80 kg weight category in chest CT examinations.

Discussion: We adjusted our age-based CT procedures in the current study to comply with the new European recommendations, Radiation Protection No. 185 (RP 185), which recommends weight groups for body CT examinations and particular age groups for head CT examinations. Following these modifications, we utilized the newly established patient groups to gather the dosimetric data (CTDIvol and DLP) in order to determine LDRLs for pediatric patients who had CT exams of the head, chest, and AP. To the best of our knowledge, the suggested LDRLs are the first nationwide attempt, in accordance with pediatric DRLs' age-weight-based methodologies, and constitute a baseline for national DRLs (NDRLs), which will be decided by this country's authorized authority. It sets the baseline for regular clinical audits within the department and encourages other facilities to do the same to standardize CT pediatric procedures. Currently, there are no comparisons throughout the entire nation. At the European level, it seems that a lot of work needs to be done to meet the new requirements.

Conclusion: The newly weight-based protocols for body CT examinations provided lower radiation doses than the age-based protocols, better reflecting the wide range of pediatric patients. Further CT optimization is needed for the heavier patients (50-80 kg).