DRL review process
A key objective of the diagnostic reference level program is to ensure that the DRLs reflect current practice, which requires ongoing monitoring and periodic updates. In Australia, ARPANSA oversees DRL monitoring through data collection via the National Diagnostic Reference Level Service (NDRLS). A liaison panel, consisting of members from relevant professional organisations, reviews data from the NDRLS MDCT survey to set updated DRLs.
The MDCT DRLs went through this review process in late 2024 and early 2025. The issues considered by the liaison panel, and their subsequent decisions, are summarised below:
Addition or removal of scan types from the list of national DRLs
The panel decided to retain all 8 existing scan types for adults and incorporate 2 additional ones: paranasal sinuses and low-dose CT (LDCT) chest. This is to ensure comprehensive data collection from CT scan types that involve the highest radiation exposure to the population. Medicare claims for all scan types were considered in setting the list of National DRLs. It was resolved to limit the number of scan types included to a maximum of 10 due to the administrative burden associated with conducting DRL comparisons.
Update of the Australian Adult CT DRLs
The panel decided to update the adult DRLs based on the data collected from over 600 facilities in the 2023 calendar year. The data collected through the NDRLS MDCT portal showed a significant reduction in radiation dose metrics used to perform diagnostic scans for all scan types for which data was collected. The panel also decided on DRLs for the two new scan types. The DRLs for paranasal sinuses are based on published DRLs from the UK which best aligned with clinical practice in Australia. The DRLs for low-dose CT (LDCT) chest are based on published information for the National Lung Cancer Screening Program (NLCSP) which began in July 2025 and the AAPM Lung Cancer Screening CT Protocols Version 6.0.
Update of the Australian Paediatric CT DRLs
The panel has resolved to update the paediatric DRLs in accordance with the recommendations outlined in ICRP Publication 135. Paediatric DRLs will now be established for multiple age bands for head scans, while DRLs for body CT scans will be categorised by various weight bands. This adjustment represents a considerable shift from the previous DRL age groupings of 0-4 years and 5-14 years, as instituted by ARPANSA in 2012. Adoption of this more detailed approach to the paediatric DRLs will better represent the scanned patient cohort, and the impact of technique parameters based on patient size.
The updated Australian paediatric DRLs are based on data submitted to the NDRLS from 2018-2023 and published international DRLs from the UK and European Union.
New NDRLS paediatric data collection method
Paediatric data submissions to the NDRLS will change to an Excel workbook model, which can be found here:
The workbook will assist facilities to easily compare radiation doses used in paediatric CT scans against the new age- and weight-based DRLs. The workbook covers all the age or weight bands in a single sample for each scan type (head, chest and abdomen-pelvis) to simplify the data collection and comparison process. Participating facilities are requested to email their completed workbooks to ndrld@arpansa.gov.au by 31 December each year, so that the data can contribute to the monitoring and future updating of the Australian paediatric DRLs.
Necessary image quality must not be compromised
Since the national DRLs have been reduced for adults (by around 10-20%) and modified for children, it is acknowledged that there will be an increase in the number of facilities exceeding these levels. It is important to emphasise that the DRLs are reference benchmarks and not dose limits. Being above the DRL is not necessarily bad practice, instead it is a prompt to check whether improvements can be made, i.e. to initiate an optimisation process. It is vital that the image quality required for the diagnostic task is maintained and this should not be sacrificed just to remain below the DRL. Facilities exceeding the DRL should seek assistance on possible optimisation by liaising with their medical physicist, CT applications specialist and radiologist/s and document their investigation.
Transition to the updated DRLs
The ARPANSA NDRLS MDCT portal will be adjusted on 1 July 2025 to enable surveys to be compared against the updated MDCT DRLs. Adult surveys started before 1 July 2025 but completed after the portal adjustment will be compared against the updated DRLs. Paediatric surveys started before 1 July 2025 but completed after the portal adjustment will be compared against the previous DRLs. Facilities conducting paediatric surveys are directed to use the new paediatric workbook template (see above).
Accreditors for the Diagnostic Imaging Accreditation Scheme (DIAS) have been advised to accept facility dose comparisons conducted against the existing DRLs until 31 December 2025. From 1 January 2026, as part of an application for accreditation (including re-accreditation), accreditors will require evidence that policies for undertaking a DRL comparison have been revised to include the updated MDCT DRLs, and that audits conducted after 1 January 2026 have been compared against the updated MDCT DRLs.
State and territory radiation regulatory authorities have also been briefed on the changes through discussions within ARPANSA’s Radiation Health Committee. ARPANSA has requested the radiation regulatory authorities to accept dose comparisons conducted against the existing DRLs until 31 December 2025 and require that audits conducted after 1 January 2026 be compared against the updated DRLs.
