The São Paulo Radiology Society’s Radiological Protection Study Group was held on November 8, about the theme “DRL: why and how to start?”. The presentation was led by physicists Isabella Paziam Fernandes Nunes and Julliana Cristina de Oliveira Castro.

DRL is the reference level in diagnosis and was introduced by the International Commission on Radiological Protection (ICRP). Since 1990, has been talking about the subject and stipulates what radiologists should be aware of. Below, what was presented each year:

• 1990 – ICRP 60: Optimization recommendations using dose constraints or investigation levels;
• 1996 – ICRP 73: Expanded reference level concepts, the introduction of the term DRL;
• 2007 – ICRP 103: Presentation of concepts in greater detail;
•  2013 – ICRP 135: DRL Terms – investigation level, DRL magnitude, DRL value and process to establish DRL;
• 2021 – ICRP 147: Quantities most suitable for radiological protection – absorbed dose x equivalent or effective dose.

As seen in ICRP 135, DRL is not the dose limit itself but rather a concept that references a group of similar characteristics and the standard value for specific procedures. Its purpose is to identify values of DRL quantities below or above, unjustifiably. Even so, the quality of the exams remains the most important in this process; that is, the dose value can not be limited by sacrificing a good image.

 DRL in radiological protection

Establishing the DRL is essential to strengthening radiological protection with patients. The EuroSafe Imaging Call for Action, an initiative carried out in 2018, created the Bonn Call for Action, highlighting 10 essential actions for strengthening radiological protection until 2022. They are:

1. Enhance the implementation of the principle of justification;
2. Enhance the implementation of the principle of optimization of protection and safety;
3. Strengthen manufacturers’ role in contributing to the overall safety regime;
4. Strengthen radiation protection education and training of health professional;
5. Shape and promote a strategic research agenda for radiation protection in medicine;
6. Increase availability of improved global information on medical exposures and occupational exposures in medicine;
7. Improve prevention of medical radiation incidents and accidents;
8. Strengthen radiation safety culture in health care;
9. Foster an improved radiation benefit-risk-dialogue;
10. Strengthen the implementation of safety requirements globally

Four points are needed to introduce DRL into the service: establish (according to the characteristics of the institution), compare (local or national values), corrective actions (unjustified values above or below reference levels), and review (periodically and consider restoration) – all work as a cycle.