I understand that ALARA as a concept was to ensure continued radiation protection of Radiation Workers and general public. Limits are a higher end metric and by keeping the doses As Low As Reasonably Achievable, by the use of Constraints, ensures that the doses are well below the regulatory limits and hence complies with the Optimization principle.
I have come across use of the synonym ALARA for Medical Exposures.(i.e. to patients and bio medical volunteers). Optimization is important in Medical Exposures and has most relevance for Radio-diagnosis, i.e., to obtain appropriate diagnostic information with least radiation dose. This is best ensured by the medical practitioner and following DRLs. Thus, I am not sure how ALARA has any role in Medical Exposures because we do not want the dose to the patient to be As Low As Reasonably Achievable, rather As Optimum As Possible, enough to get the maximum diagnostic information.
ALARA of course continues to have relevance to the medical practitioners and the public around the facility.
Request you to provide your views and whether my understanding is in line with the experts.
You are correct in your interpretation that Optimization of radiation doses for patients focuses on using the least amount of radiation exposure to the patient to achieve a diagnostically appropriate image or appropriate therapeutic outcome. This interpretation is reinforced in paragraph 65 of International Commission on Radiological Protection (ICRP) Publication 139, Occupational radiological protection in interventional procedures[1]. The use of the As Low As Reasonably Achievable (ALARA) standard in the medical environment with regard to patient exposure must be balanced with ensuring that the imaging or therapeutic outcome is clinically appropriate. One might summarize this risk management process as “use as much radiation exposure as is necessary to achieve the clinical outcome, but no more”. The principle of Limitation does not apply to medical patients.
You are also correct that the application of the ALARA standard in the medical environment remains relevant for controlling occupational and public exposure. While the principle of Limitation is important to prevent radiation injury to workers and members of the public, the use of the Optimization principle which includes the ALARA standard serves to reduce the risk of future unintended effects of radiation exposure. In Position Statement PS013-1, Occupational Radiation Safety Standards and Regulations Are Sound, the Health Physics Society recognizes that the incorporation of the ALARA standard into US state and federal radiation control regulations has resulted in individual doses to the vast majority of workers being controlled to levels much less than the regulatory limits. The Health Physics Society also supports the use of the ALARA standard in controlling radiation exposure to the public. Refer to Position Statement PS-0005-3, Ionizing Radiation Safety Standards for the General Public.
Michael Lewandowski, CHP, FHPS,
Health Physics Society President 2025-2027
[1] ICRP, 2018. Occupational radiological protection in interventional procedures. ICRP Publication 139. Ann. ICRP 47(2).
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