Connections between categories of exposure in the hospital setting

Abstract

Actions that ensure the radiological protection of staff and members of the public are often interconnected with those dedicated to the radiological protection of patients in hospital settings. For example, the staff radiation exposure in nuclear medicine and interventional radiology is related to the dose absorbed by the patient. Moreover, it is important to underline that the justification for everyone's exposure is largely driven by patient benefit. In this scenario, provisions to protect staff and the public should not impair those to optimise patient exposure or, more generally, limit clinical outcome. However, the presence of different categories of exposure is often reflected in regulatory systems where the management of the protection of patients and workers/members of the public can be quite separated. This scenario represents a weakness in the application of the radiological protection system in hospitals. In this article, some workers’ exposure pathways in medical practices are described, also reporting what is already provided in ICRP Publication 139 on this topic. Finally, a proposal is made to facilitate the practical implementation of the system, with the intention of stimulating discussion.

1. INTRODUCTION

One of the pillars for the application of the radiological protection system is the choice of defining three different categories of exposure. In this regard, two excerpts from ICRP Publication 103 (ICRP, 2007) are reported below, where the rationale behind this choice is summarised:

(170) The assumed proportional relationship between an increment of dose and an increment of risk of stochastic effects makes it possible to deal separately with different parts of this network of events and situations leading to exposure, and to select those parts that are of relevance in a given situation. To make these selections, however, it is necessary to define, for each part of the network, the objectives, the organisations (and individuals) responsible for protection, the lines of responsibility, and the feasibility of obtaining the necessary information. This remains a complex procedure, and the Commission suggests two simplifications in managing radiological situations.

(171) The first simplification was used in the 1990 Recommendations and recognises that individuals are subject to several categories of exposure, which can be dealt with separately (ICRP, 1991b). For example, most workers who are exposed to radiation sources as part of their work are also exposed to environmental sources as members of the public, and to medical exposure as patients. The Commission's policy continues to be that the control of exposures due to work need not be influenced by the exposures from these other sources. This policy is still generally reflected in the present Recommendations by the separation of the exposure into three categories (see Section 5.3): occupational exposure, medical exposure of patients, and public exposure. The Commission continues to recommend that, for regulatory purposes, no attempt be made to add the exposures to the same individual from the different categories of exposure.

This recommendation is often reflected in regulatory systems where the management of the protection of patients and workers/public can be quite separated. For example, different professionals may be involved, as provided for in Directive 2013/59/Euratom, which defines the radiation protection expert (RPE) and the medical physics expert (MPE), the former dealing with the physical aspects of radiological protection of workers and members of the public and the latter of patients (EU Council, 2013). Moreover, the optimisation principle can be applied in practice through separate provisions for the different categories of exposure, also when they occur simultaneously during the same practice or are interconnected, as it happens in hospital settings.

2. THE PROBLEM

In practise, the exposure of staff and members of the public in hospitals is related to patients’ exposure. For example, in interventional radiology, staff exposure mainly depends on radiation scattered by the patient. Therefore, staff exposure depends on many parameters that are crucial in patients’ exposure (imaging protocols, collimation, frame rate, dose rate, etc.) as all these parameters can influence the clinical outcome.

A similar scenario can be found in nuclear medicine, where the patient is injected with a radioactive tracer and has to be assisted.

A schematic representation of the exposure pathway in these two examples can be found in Fig. 1. A source of ionising radiation is used on the patient for diagnostic or therapeutic purposes: a medical exposure occurs. Subsequently, occupational exposure occurs mainly due to radiation scattered by the patient in interventional radiology and radiation emitted by the patient as a result of radiopharmaceutical injection in nuclear medicine. In these cases, there is one source, one practice, one exposure pathway, and two strategies of protection, one for the staff and one for the patient. This makes the practical application of the radiological protection system complex, redundant, and sometimes unclear, especially when the areas of action of, for example, RPE and MPE overlap. In fact, the provisions to protect the staff from the harmful effects of ionising radiation, established by the RPE, may not be aligned with those established by the MPE to protect the patient.

Fig. 1.

Schematic representation of the exposure pathways in interventional radiology (upper) and nuclear medicine (lower): in both cases medical and occupational exposure is part of the same practice and of the same exposure pathway.

Moreover, the presence of two strategies of protection makes the practical application of the optimisation principle complex, as it can be adequately applied only considering the practice as a whole. For example, in interventional radiology, every time the imaging protocol is modified to optimise the medical exposure, the exposure of the staff is also influenced. In this scenario, staff exposure cannot be adequately controlled without considering patient exposure. Summarising, the existence of different categories of exposure is reflected in regulatory systems where the management of the protection of patients and workers/members of the public can be quite separated, while in practice exposures optimisation requires a deeply integrated approach.

Furthermore, it is important to emphasise that the exposure of all, patients, workers, and, where appropriate, members of the public, is justified by the benefit to the patient. Therefore, provisions dedicated to the protection of all should not limit the clinical outcome and should be finally approved by healthcare professionals.

These are just two simple examples of the connection between categories of exposure in the medical field; there are many others where the connection does not imply that the patient becomes a source of exposure for the staff and for which similar considerations can be equally applied.

3. THE PROPOSAL

The need for an integrated approach to the management of radiological protection in the hospital setting has already been addressed by the ICRP. For example, ICRP Publication 139, devoted to interventional radiology, states the following (ICRP, 2018):

Occupational exposure in interventional procedures is closely related to patient exposure and, therefore, management of occupational protection should be integrated with patient protection. … Measures to protect staff should not impair the clinical outcome, and should not increase patient exposure.

Similarly, the Directive 2013/59/Euratom states that ‘The radiation protection expert shall, where appropriate, liaise with the medical physics expert’ (EU Council, 2013), implicitly recognising that provisions for the protection of workers, members of the public, and patients should be defined taking into account the interconnections between the different categories of exposure.

Whereas an integrated approach to radiological protection in hospitals has also been identified as important in practices other than interventional radiology by a regional organisation (Byrne B et al., 2023), the author proposes to generalise what has been reported in ICRP Publication 139 (ICRP, 2018) to all medical practices:

In the medical field, the justification for the exposure of workers and general public is mainly driven by the patient benefit. Therefore, radiological protection provisions for workers and members of the public exposed as a result of medical exposures should be managed in an integrated manner with patient exposure.

In particular, provisions dedicated to workers and public protection should not limit the clinical outcome and should take into account the interconnections between patient and staff/members of the public exposures, to ensure an adequate application of the optimisation principle.

This proposal was presented during the ICRP 2023 Symposium in Tokyo to stimulate debate and obtain feedback.