The draft report Practical Aspects of Radiological Protection in Digital Radiography, Fluoroscopy and CT, follows on the heels of another draft report (Ref 4859-1536-0025) Optimisation of Radiological Protection in Digital Radiology Techniques for Medical Imaging. The contents of both reports indicate that ICRP appears to have undergone a paradigm shift in its approach to the provision of guidance on radiological protection of the patient in medicine. These documents contain detailed advice related to Quality Assurance (QA), Quality Control (QC) and the application of Quality Management Systems (QMS). This shift could have possible future consequences for radiological protection in general. Also, the validity of this shift depends on the exact meaning of terminology employed by ICRP and the radiation protection community in general.
Agencies such as IAEA, NCRP, NEMA, European Union in the EURATOM Programme, European Society of Radiology as well as the US Occupational Safety and Health Administration, Royal College of Radiology, to name but a few, all employ the term radiation protection to describe the field of endeavour covered by ICRP. Equally, an enormous body of scientific literature and published documents have employed this term over many years. Indeed, ICRP also employed this term itself prior to Publication 55 in 1989.
However, ICRP now employs the term radiological protection, which has a much broader connotation than the term radiation protection, especially in respect of protection of the patient in the medical field of diagnostic radiology. The Oxford dictionary defines radiological as “relating to the science of X-rays and other high energy radiation”. Here science is taken to mean:
…(knowledge from) the careful study of the structure and behaviour of the physical world, especially by watching, measuring, and doing experiments, and the development of theories to describe the results of these activities.
Hence, does the science of X-rays equate to the science of medical imaging when ionising radiations are employed?
If so, from a radiological protection perspective, the risks to patients in diagnostic radiology comprise two inter-related components. The radiation risk arising from use of ionising radiation on patients and the diagnostic risks arising from the outcome of a clinical procedure due to inadequate imaging techniques and/or procedures as well as incorrect diagnosis. Both fall within the scope of the science of X-rays in patient care and thus, the use of the term radiological protection implies activities that protect patients from both types of risk and thus contribute to the overall efficacy of an examination. Whereas, didactically, radiation protection implies actions that are concerned with the protection of the worker, the general-public and patients from the ionising radiation employed. Historically, the ALARA principle has embodied this concept.
The draft document under consideration meets the more general criterion since the application of QA, QC and QMS can help, in the fullest sense of the word, to ensure that a patient receives the best possible diagnostic examination from both the perspective of dose and image quality. They are components of the underlying science of medical imaging, which includes factors that can affect the outcome from an examination. However, this paradigm shift means that ICRP has strayed into the provision of advice that relates to the efficacy of activities that employ ionising radiation rather than advice aimed primarily at keeping doses As Low AS Reasonably Achievable! In fact, within the draft document ICRP has proposed a multi-level approach to optimisation (ranging from D: Preliminary to A: Advanced). A corollary to this is that the justification of examinations that are undertaken at higher levels of optimisation must be higher, certainly from an ethical perspective, since the probability of a better outcome should be increased. Incidentally, this would imply that justification could be treated as a “proportionate variable”, as discussed in the publication “A Review of the Scientific Basis for Radiation Protection of the Patient” (B.M.Moores and D. Regulla, Radiation Protection Dosimetry, Vol 147, Nos 1-2, 22-29, 2011).
Ionising radiations are employed in numerous other fields including non-destructive testing, nuclear power generation, construction as well as medical and dental applications. If the much broader approach to protection advice contained in the draft document (Ref 4854-2345-7344), is accepted as the way forward then similar types of guidance would be just as relevant to these other activities. For example, in the case of non-destructive testing, radiation risks are dependent upon the design and construction of the facility including the effectiveness of the imaging system employed as well as operating procedures. Poor quality imaging can lead to rejected images and repeat exposures hence greater risks for a given level of protection. For example, this would be most noticeable in field work where less stringent protection measures might apply.
QA, QC and QMS play important roles in the maintenance of safe standards of working as well as the production adequate levels of image quality at acceptable dose levels and thus are an integral part of overall radiological safety including the optimisation of practices. Indeed, such an approach is relevant to all sectors that employ ionising radiation including the nuclear industry. A nuclear reactor that consistently runs below its designed power output level does not represent an optimised process from a benefit-risk perspective. Therefore, can we expect ICRP to provide similar guidance on the optimisation of radiological processes through advice on QA, QC and QMS to the many other fields that employ ionising radiations?
There are other possible consequences from this new approach in terms of the future nature of relevant advice and guidance. For example, the application of Artificial Intelligence (AI) and Machine Learning (ML) techniques to optimisation are mentioned in both draft reports (Ref 4854-2345-7344) and (Ref 4859-1536-0025). At some stage QA and QC techniques may be required to ensure that AI methods themselves perform satisfactorily, whether they are applied to the assessment of image quality or perform clinical image reading tasks. A reduction in technical repeats and recalls of 78% has already been noted when AI is applied to the quantification of mammography image quality. Are we to assume that ICRP will, at some stage, provide advice and guidance on the use and performance of AI techniques as part of optimisation, for example will minimum standards of performance be expected from such systems?
It is possible that within the many other fields that employ ionising radiation AI techniques may play important roles in both optimisation and safety, which ensures the best possible outcomes, including the levels of radiation received, whether by workers, the general-public or the environment. ICRP has now set a precedent in providing specific and detailed advice and guidance on optimisation of practices that employ ionising radiations through the application of QA, QC and QMS.
ICRP is at present undertaking a review of the system of radiological protection. The review should not only clarify the correct terminology to describe the field of endeavour covered by ICRP but also indicate whether the new approach to guidance on radiological protection in medicine will be applied to the many other fields that involve the use of ionising radiations.