Exposure to MRI-related magnetic fields and vertigo in MRI workers

Induced electric fields in MRI settings and electric vestibular stimulations: same vestibular effects?

In Magnetic Resonance Imaging scanner environments, the continuous Lorentz Force is a potent vestibular stimulation. It is nowadays so well known that it is now identified as Magnetic vestibular stimulation (MVS). Alongside MVS, some authors argue that through induced electric fields, electromagnetic induction could also trigger the vestibular system. Indeed, for decades, vestibular-specific electric stimulations (EVS) have been known to precisely impact all vestibular pathways. Here, we go through the literature, looking at potential time varying magnetic field induced vestibular outcomes in MRI settings and comparing them with EVS-known outcomes. To date, although theoretically induction could trigger vestibular responses the behavioral evidence remains poor. Finally, more vestibular-specific work is needed.

Health risks for medical personnel due to magnetic fields in magnetic resonance imaging

The current state of medical and scientific knowledge on the effects of exposure to electromagnetic fields on workers in the field of clinical magnetic resonance imaging (MRI) is summarized here.A systematic literature search was conducted to analyze the health risks to medical personnel from magnetic fields in MRI. A total of 7273 sources were identified, with 7139 being excluded after screening of the title and abstract. After full-text screening, 34 sources remained and were included in this paper.There are a number of scientific publications on the occurrence of short-term sensory effects such as vertigo, metallic taste, phosphenes as well as on the occurrence of neurocognitive and neurobehavioral effects. For example, short-term exposure to clinical magnetic fields has been reported to result in a 4% reduction in speed and precision and a 16% reduction in visual contrast sensitivity at close range. Both eye-hand precision and coordination speed are affected. The long-term studies concern, among other things, the influence of magnetic fields on sleep quality, which could be linked to an increased risk of accidents. The data on the exposure of healthcare workers to magnetic fields during pregnancy is consistently outdated. However, it has been concluded that there are no particular deviations with regard to the duration of pregnancy, premature births, miscarriages, and birth weight. Epidemiological studies are lacking. With a focus on healthcare personnel, there is a considerable need for high-quality data, particularly on the consequences of long-term exposure to electromagnetic fields from clinical MRI and the effects on pregnancy. · Short-term sensory effects such as vertigo, metallic taste, phosphenes as well as neurocognitive and neurological behavioral effects may occur upon exposure to magnetic fields.. · Long-term effects mainly concern quality of sleep, which can be associated with an increased risk of accidents.. · When pregnant women were exposed to magnetic fields, no particular deviations were found with regard to the duration of pregnancy, premature births, miscarriages, and birth weight.. · König AM, Pöschke A, Mahnken AH. Health risks for medical personnel due to magnetic fields in magnetic resonance imaging. Fortschr Röntgenstr 2024; DOI 10.1055/a-2296-3860.

Is activation of the vestibular system by electromagnetic induction a possibility in an MRI context?

In recent years, an increasing number of studies have discussed the mechanisms of vestibular activation in strong magnetic field settings such as occur in a magnetic resonance imaging scanner environment. Amid the different hypotheses, the Lorentz force explanation currently stands out as the most plausible mechanism, as evidenced by activation of the vestibulo-ocular reflex. Other hypotheses have largely been discarded. Nonetheless, both human data and computational modeling suggest that electromagnetic induction could be a valid mechanism which may coexist alongside the Lorentz force. To further investigate the induction hypothesis, we provide, herein, a first of its kind dosimetric analysis to estimate the induced electric fields at the vestibular system and compare them with what galvanic vestibular stimulation would generate. We found that electric fields strengths from induction match galvanic vestibular stimulation strengths generating vestibular responses. This review examines the evidence in support of electromagnetic induction of vestibular responses, and whether movement-induced time-varying magnetic fields should be further considered and investigated.

Refocusing on work-based hazards for the anaesthesiologist in a post-pandemic era

The coronavirus pandemic has raised public awareness of one of the many hazards that healthcare workers face daily: exposure to harmful pathogens. The anaesthesia workplace encompasses the operating room, interventional radiology suite, and other sites that contain many other potential occupational and environmental hazards. This review article highlights the work-based hazards that anaesthesiologists and other clinicians may encounter in the anaesthesia workplace: ergonomic design, physical, chemical, fire, biological, or psychological hazards. As the anaesthesia work environment enters a post-COVID-19 pandemic phase, anaesthesiologists will do well to review and consider these hazards. The current review includes proposed solutions to some hazards and identifies opportunities for future research.

Longer duration entry mitigates nystagmus and vertigo in 7-Tesla MRI

Introduction

Patients and technologists commonly describe vertigo, dizziness, and imbalance near high-field magnets, e.g., 7-Tesla (T) magnetic resonance imaging (MRI) scanners. We sought a simple way to alleviate vertigo and dizziness in high-field MRI scanners by applying the understanding of the mechanisms behind magnetic vestibular stimulation and the innate characteristics of vestibular adaptation.

Methods

We first created a three-dimensional (3D) control systems model of the direct and indirect vestibulo-ocular reflex (VOR) pathways, including adaptation mechanisms. The goal was to develop a paradigm for human participants undergoing a 7T MRI scan to optimize the speed and acceleration of entry into and exit from the MRI bore to minimize unwanted vertigo. We then applied this paradigm from the model by recording 3D binocular eye movements (horizontal, vertical, and torsion) and the subjective experience of eight normal individuals within a 7T MRI. The independent variables were the duration of entry into and exit from the MRI bore, the time inside the MRI bore, and the magnetic field strength; the dependent variables were nystagmus slow-phase eye velocity (SPV) and the sensation of vertigo.

Results

In the model, when the participant was exposed to a linearly increasing magnetic field strength, the per-peak (after entry into the MRI bore) and post-peak (after exiting the MRI bore) responses of nystagmus SPV were reduced with increasing duration of entry and exit, respectively. There was a greater effect on the per-peak response. The entry/exit duration and peak response were inversely related, and the nystagmus was decreased the most with the 5-min duration paradigm (the longest duration modeled). The experimental nystagmus pattern of the eight normal participants matched the model, with increasing entry duration having the strongest effect on the per-peak response of nystagmus SPV. Similarly, all participants described less vertigo with the longer duration entries.

Conclusion

Increasing the duration of entry into and exit out of a 7T MRI scanner reduced or eliminated vertigo symptoms and reduced nystagmus peak SPV. Model simulations suggest that central processes of vestibular adaptation account for these effects. Therefore, 2-min entry and 20-s exit durations are a practical solution to mitigate vertigo and other discomforting symptoms associated with undergoing 7T MRI scans. In principle, these findings also apply to different magnet strengths.

Radiographers' awareness level of MRI-induced vertigo and their perspectives on the post-examination care provided to patients in Saudi Arabia

INTRODUCTION

Vertigo has been reported by operators and patients during magnetic resonance imaging (MRI) examinations and found to increase in severity as the strength of the scanner magnet increases. This study examined a cohort of MRI radiographers' awareness of MRI-induced vertigo and their perspectives on post-MRI care.

METHODS

This cross-sectional study used a web-based survey distributed to 110 radiographers. The 18-item survey included questions to elicit demographic information, MRI radiographers' awareness of MRI-induced vertigo, and their perspectives on the post-MRI care that should be provided to patients. Responses were collected between June 2021 and January 2022. The collected data were analyzed using SPSS, version 27.

RESULTS

A total of 110 MRI radiographers completed the survey. Participants were predominantly male (64.5 %) and working in public practice (91.8 %). Almost all the radiographers were aware of MRI-induced vertigo. About two-thirds of participants knew patients needed assistance off the couch. Nearly all participants knew patients should be asked about their experience with MRI-induced vertigo after their procedures. There were statistically significant associations between the size of magnetic field strength used by the participants and their appreciation of the needed support for patients post-MRI examinations (p= 0.012).

CONCLUSION

This study provides the first insight into Saudi Arabian MRI radiographers' awareness and perceptions of MRI-induced vertigo. Radiographers were largely aware of MRI-induced vertigo and the supportive care they were supposed to provide their patients.

IMPLICATIONS FOR PRACTICE

The current study points to a need for training to expand awareness levels of MRI-induced vertigo among a few Saudi MRI radiographers.

Health effects related to exposure of static magnetic fields and acoustic noise-comparison between MR and CT radiographers

OBJECTIVES

We explored the prevalence of health complaints subjectively associated with static magnetic field (SMF) and acoustic noise exposure among MR radiographers in Sweden, using CT radiographers as a control group. Additionally, we explored radiographers' use of strategies to mitigate adverse health effects.

METHODS

A cross-sectional survey was sent to all hospitals with MR units in Sweden. MR and/or CT personnel reported prevalence and attribution of symptoms (vertigo/dizziness, nausea, metallic taste, illusion of movement, ringing sensations/tinnitus, headache, unusual drowsiness/tiredness, forgetfulness, difficulties concentrating, and difficulties sleeping) within the last year. We used logistic regression to test associations between sex, age, stress, SMF strength, working hours, and symptom prevalence. Data regarding hearing function, work-environmental noise, and strategies to mitigate adverse symptoms were also analysed.

RESULTS

In total, 529 out of 546 respondents from 86 hospitals were eligible for participation. A ≥ 20 working hours/week/modality cut-off rendered 342 participants grouped into CT (n = 75), MR (n = 121), or mixed personnel (n = 146). No significant differences in symptom prevalence were seen between groups. Working at ≥ 3T increased SMF-associated symptoms as compared with working at ≤ 1.5T (OR: 2.03, CI95: 1.05-3.93). Stress was a significant confounder. Work-related noise was rated as more troublesome by CT than MR personnel (p < 0.01). MR personnel tended to use more strategies to mitigate adverse symptoms.

CONCLUSION

No significant differences in symptom prevalence were seen between MR and CT radiographers. However, working at 3T increased the risk of SMF symptoms, and stress increased adverse health effects. Noise nuisance was considered more problematic by CT than MR personnel.

KEY POINTS

• No significant differences in symptom prevalence were seen between MR and CT radiographers. • Working at ≥ 3 T doubled the odds of experiencing SMF symptoms (vertigo/dizziness, nausea, metallic taste, and/or illusion of movement) as compared to working exclusively at ≤ 1.5 T. • Work-related acoustic noise was less well mitigated and was rated as more troublesome by CT personnel than by MR personnel.

Vestibular Extremely Low-Frequency Magnetic and Electric Stimulation Effects on Human Subjective Visual Vertical Perception

Electric fields from both extremely low‐frequency magnetic fields (ELF‐MF) and alternating current (AC) stimulations impact human neurophysiology. As the retinal photoreceptors, vestibular hair cells are graded potential cells and are sensitive to electric fields. Electrophosphene and magnetophosphene literature suggests different impacts of AC and ELF‐MF on the vestibular hair cells. Furthermore, while AC modulates the vestibular system more globally, lateral ELF‐MF stimulations could be more utricular specific. Therefore, to further address the impact of ELF‐MF‐induced electric fields on the human vestibular system and the potential differences with AC stimulations, we investigated the effects of both stimulation modalities on the perception of verticality using a subjective visual vertical (SVV) paradigm. For similar levels of SVV precision, the ELF‐MF condition required more time to adjust SVV, and SVV variability was higher with ELF‐MF than with AC vestibular‐specific stimulations. Yet, the differences between AC and ELF‐MF stimulations were small. Overall, this study highlights small differences between AC and ELF‐MF vestibular stimulations, underlines a potential utricular contribution, and has implications for international exposure guidelines and standards. © 2022 Bioelectromagnetics Society.

Short- and long-term effects of 3.5-23.0 Tesla ultra-high magnetic fields on mice behaviour

OBJECTIVES

Higher static magnetic field (SMF) enables higher imaging capability in magnetic resonance imaging (MRI), which encourages the development of ultra-high field MRIs above 20 T with a prerequisite for safety issues. However, animal tests of ≥ 20 T SMF exposure are very limited. The objective of the current study is to evaluate mice behaviour consequences of 3.5-23.0 T SMF exposure.

METHODS

We systematically examined 112 mice for their short- and long-term behaviour responses to a 2-h exposure of 3.5-23.0 T SMFs. Locomotor activity and cognitive functions were measured by five behaviour tests, including balance beam, open field, elevated plus maze, three-chamber social recognition, and Morris water maze tests.

RESULTS

Besides the transient short-term impairment of the sense of balance and locomotor activity, the 3.5-23.0 T SMFs did not have long-term negative effects on mice locomotion, anxiety level, social behaviour, or memory. In contrast, we observed anxiolytic effects and positive effects on social and spatial memory of SMFs, which is likely correlated with the significantly increased CaMKII level in the hippocampus region of high SMF-treated mice.

CONCLUSIONS

Our study showed that the short exposures to high-field SMFs up to 23.0 T have negligible side effects on healthy mice and may even have beneficial outcomes in mice mood and memory, which is pertinent to the future medical application of ultra-high field SMFs in MRIs and beyond.

KEY POINTS

• Short-term exposure to magnetic fields up to 23.0 T is safe for mice. • High-field static magnetic field exposure transiently reduced mice locomotion. • High-field static magnetic field enhances memory while reduces the anxiety level.

Subjective symptoms of SMFs and RF energy, and risk perception among staff working with MR scanners within two public hospitals in South Africa

This study assessed subjective symptoms associated with exposure to static magnetic fields (SMFs) and radiofrequency (RF) energy, and perceived safety risk of scanners among magnetic resonance (MR) staff working in the 1.5 and 3 T MRI units. A questionnaire survey was completed by 77 clinical imaging staff working in two hospitals (A and B) in the Mangaung metropolitan region. 50 participants working with the MR scanners were regarded as exposed group and 27 participants from CT scan and X-ray departments were classified as control group. The study comprised 57% females and 43% male participants with an average MRI experience of 5.4 years. Using logistic regression, tinnitus was significantly different between various job titles (p< .034) and it was reported more often (OR 8:00; CI 1.51, 15.17) by those who worked on a 3 T scanner. Increased years of MRI experience was a significant predictor of headache (p< .05), and reporting of nausea was significantly different between various job titles (p < .01). There was an increased risks of reporting vertigo often among female participants (OR: 4.43; CI 0.91, 21.47), those with 5-15 years of MRI experience (OR: 2.09; CI 0.47, 9.34), and those with a light to moderate workload (OR: 2.70; CI 0.49, 14.86). Using linear regression, presence in zone IV during image acquisitioning was the only significant predictor for the sensation of glowing (p < .000). Movement of head/ upper body in the scanner bore was a significant predictor of nausea (p< .026), vertigo (p< .014), instability when standing (p< .014), and a metallic taste (p< .031). There was no correlation between reporting of symptoms and perceived risk of scanners. However, shift duration (r_s = 0.576), movement of head/upper body in the scanner bore (r_s = 0.424), and strength of the scanners (r_s = 0.299) were significantly correlated with perceived risk of scanners. MRI safety training and a comprehensive occupational health and safety program are necessary.

Electromagnetic Exposure of Personnel Involved in Cardiac MRI Examinations in 1.5T, 3T and 7T Scanners

(1) Background: It has been hypothesised that a significant increase in the use of cardiac magnetic resonance (CMR), for example, when examining COVID-19 convalescents using magnetic resonance imaging (MRI), has an influence the exposure profiles of medical personnel to static magnetic fields (STmf). (2) Methods: Static exposure to STmf (SEmf) was recorded during activities that modelled performing CMR by radiographers. The motion-induced time variability of that exposure (TVEmf) was calculated from SEmf samples. The results were compared with: (i) labour law requirements; (ii) the distribution of vertigo perception probability near MRI magnets; and (iii) the exposure profile when actually performing a head MRI. (3) Results: The exposure profiles of personnel managing 42 CMR scans (modelled using medium (1.5T), high (3T) and ultrahigh (7T) field scanners) were significantly different than when managing a head MRI. The majority of SEmf and TVEmf samples (up to the 95th percentile) were at low vertigo perception probability (SEmf < 500 mT, TVEmf < 600 mT/s), but a small fraction were at medium/high levels; (4) Conclusion: Even under the “normal working conditions” defined for SEmf (STmf < 2T) by labour legislation (Directive 2013/35/EC), increased CMR usage increases vertigo-related hazards experienced by MRI personnel (a re-evaluation of electromagnetic safety hazards is suggested in the case of these or similar changes in work organisation).

Issues in the Implementation of Directive 2013/35/EU Regarding the Protection of Workers against Electromagnetic Fields

In 2016 the Directive 2013/35/EU regarding the protection of health and safety of workers exposed to electromagnetic fields was transposed in Italy. Since then, the authors of this paper have been faced with several issues related to the implementation of the provisions of the Directive, which pose some interpretative and operative concerns. A primary critical feature of the Directive is that, in some circumstances, conditions of "overexposure", i.e., of exceeding the exposure limits, are allowed. In the case of transient effects, the "flexibility" concerning the compliance with exposure limits is based on the approach introduced by ICNIRP in its guidelines on static magnetic fields and on time-varying electric and magnetic fields. On the contrary, the possibility of exceeding the exposure limits for health effects, formally recognized in the article of the Directive dealing with derogations, is not included in the ICNIRP guidelines. This paper analyzes the main concerns in interpreting and managing some provisions of the Directive with particular reference to the issue of how the employer can manage the situations of overexposure.

Subjective Symptoms in Magnetic Resonance Imaging Personnel: A Multi-Center Study in Italy

Introduction: Magnetic Resonance Imaging (MRI) personnel have significant exposure to static and low-frequency time-varying magnetic fields. In these workers an increased prevalence of different subjective symptoms has been observed. The aim of our study was to investigate the prevalence of non-specific subjective symptoms and of "core symptoms" in a group of MRI personnel working in different centers in Italy, and of possible relationships with personal and occupational characteristics. Methods: The occurrence of 11 subjective symptoms was evaluated using a specific questionnaire with 240 subjects working in 6 different Italian hospitals and research centers, 177 MRI health care and research personnel and 63 unexposed subjects employed in the same departments. Exposure was subjectively investigated according to the type of MRI scanner (≤1.5 vs. ≥3 T) and to the number of MRI procedures attended and/or performed by the personnel, even if no information on how frequently the personnel entered the scanner room was collected. The possible associations among symptoms and estimated EMF exposure, the main characteristics of the population, and job stress perception were analyzed. Results: Eighty-six percent of the personnel reported at least one symptom; drowsiness, headache, and sleep disorders were the most frequent. The total number of symptoms did not differ between exposed persons and controls. Considering the total number of annual MRI procedures reported by the personnel, no significant associations were found nor with the total number of symptoms, nor with "core symptoms." Only subjects complaining of drowsiness also reported a significantly higher mean annual number of MRI procedures with ≤ 1.5 T scanners when compared with exposed subjects without drowsiness. In a multivariate model, subjects with a high level of perceived stress complained of more symptoms (p = 0.0002). Conclusions: Our study did not show any association between the occurrence of reversible subjective symptoms, including the more specific "core symptoms," and the occupational exposure of MRI personnel to static and low-frequency time-varying magnetic fields. On the other hand, the role played by occupational stress appears to be not negligible. In further research in this field, measurements of EMF exposure should be considered.

Occupational exposure to electromagnetic fields in magnetic resonance environment: an update on regulation, exposure assessment techniques, health risk evaluation, and surveillance

Magnetic resonance imaging (MRI) is one of the most-used diagnostic imaging methods worldwide. There are ∼50,000 MRI scanners worldwide each of which involves a minimum of five workers from different disciplines who spend their working days around MRI scanners. This review analyzes the state of the art of literature about the several aspects of the occupational exposure to electromagnetic fields (EMF) in MRI: regulations, literature studies on biological effects, and health surveillance are addressed here in detail, along with a summary of the main approaches for exposure assessment. The original research papers published from 2013 to 2021 in international peer-reviewed journals, in the English language, are analyzed, together with documents published by legislative bodies. The key points for each topic are identified and described together with useful tips for precise safeguarding of MRI operators, in terms of exposure assessment, studies on biological effects, and health surveillance.

Occupational Exposure to Electromagnetic Fields and Health Surveillance According to the European Directive 2013/35/EU

In the European Union, health surveillance (HS) of electromagnetic fields (EMF)-exposed workers is mandatory according to the Directive 2013/35/EU, aimed at the prevention of known direct biophysical effects and indirect EMF's effects. Long-term effects are not addressed in the Directive as the evidence of a causal relationship is considered inadequate. Objectives of HS are the prevention or early detection of EMF adverse effects, but scant evidence is hitherto available on the specific procedures. A first issue is that no specific laboratory tests or medical investigations have been demonstrated as useful for exposure monitoring and/or prevention of the effects. Another problem is the existence of workers at particular risk (WPR), i.e., subjects with specific conditions inducing an increased susceptibility to the EMF-related risk (e.g., workers with active medical devices or other conditions); exposures within the occupational exposure limit values (ELVs) are usually adequately protective against EMF's effects, but lower exposures can possibly induce a health risk in WPR. Consequently, the HS of EMF-exposed workers according to the EU Directive should be aimed at the early detection and monitoring of the recognized adverse effects, as well as an early identification of WPR for the adoption of adequate preventive measures.

Exposure levels of radiofrequency magnetic fields and static magnetic fields in 1.5 and 3.0 T MRI units

Magnetic resonance imaging (MRI) staff is exposed to a complex mixture of electromagnetic fields from MRI units. Exposure to these fields results in the development of transient exposure-related symptoms. This study aimed to investigate the exposure levels of radiofrequency (RF) magnetic fields and static magnetic fields (SMFs) from 1.5 and 3.0 T MRI scanners in two public hospitals in the Mangaung Metropolitan region, South Africa. The exposure levels of SMFs and RF magnetic fields were measured using the THM1176 3-Axis hall magnetometer and TM-196 3 Axis RF field strength meter, respectively. Measurements were collected at a distance of 1 m (m) and 2 m from the gantry for SMFs when the brain, cervical spine and extremities were scanned. Measurements for RF magnetic fields were collected at a distance of 1 m with an average scan duration of six minutes. Friedman’s test was used to compared exposure mean values from two 1.5 T scanners, and Wilcoxon test with Bonferroni adjustment was used to identify where the difference between exist. The Shapiro–Wilk test was also used to test for normality between exposure levels in 1.5 and 3.0 T scanners. The measured peak values for SMFs from the 3.0 T scanner at hospital A were 1300 milliTesla (mT) and 726 mT from 1.5 T scanner in hospital B. The difference in terms of SMFs exposure levels was observed between two 1.5 T scanners at a distance of 2 m. The difference between 1.5 T scanners at 1 m was also observed during repeated measurements when brain, cervical spine and extremities scans were performed. Scanners’ configurations, magnet type, clinical setting and location were identified as factors that could influence different propagation of SMFs between scanners of the same nominal B0. The RF pulse design, sequence setting flip-angle and scans performed influenced the measured RF magnetic fields. Three scanners were complaint with occupational exposure guidelines stipulated by the ICNIRP; however, peak levels that exist at 1 m could be managed through adoption of occupational health and safety programs.

Peak Inhalation Exposure Metrics Used in Occupational Epidemiologic and Exposure Studies

Peak exposures are of concern because they can potentially overwhelm normal defense mechanisms and induce adverse health effects. Metrics of peak exposure have been used in epidemiologic and exposure studies, but consensus is lacking on its definition. The relevant characteristics of peak exposure are dependent upon exposure patterns, biokinetics of exposure, and disease mechanisms. The objective of this review was to summarize the use of peak metrics in epidemiologic and exposure studies. A comprehensive search of Medline, Embase, Web of Science, and NIOSHTIC-2 databases was conducted using keywords related to peak exposures. The retrieved references were reviewed and selected for indexing if they included a peak metric and met additional criteria. Information on health outcomes and peak exposure metrics was extracted from each reference. A total of 1,215 epidemiologic or exposure references were identified, of which 182 were indexed and summarized. For the 72 epidemiologic studies, the health outcomes most frequently evaluated were: chronic respiratory effects, cancer and acute respiratory symptoms. Exposures were frequently assessed using task-based and full-shift time-integrated methods, qualitative methods, and real-time instruments. Peak exposure summary metrics included the presence or absence of a peak event, highest exposure intensity and frequency greater than a target. Peak metrics in the 110 exposure studies most frequently included highest exposure intensity, average short-duration intensity, and graphical presentation of the real-time data (plots). This review provides a framework for considering biologically relevant peak exposure metrics for epidemiologic and exposure studies to help inform risk assessment and exposure mitigation.

Analysis, comparison and representation of occupational exposure to a static magnetic field in a 3-T MRI site

The purpose of this study is to analyze exposure to the time-varying magnetic field caused by worker movements in a 3-T clinical magnetic resonance imaging (MRI) scanner. Measurements of the static magnetic field (B) in the proximity of the MRI scanner were performed to create a detailed map of the spatial gradient of B, in order to indicate the areas at high risk of exposure. Moreover, a personal exposure recording system was used in order to analyze and compare exposure to the static magnetic field during different routine procedures in MRI. We found that for all of the performed work activities, exposure was compliant with International Commission on Non-Ionizing Radiation Protection levels. However, our findings confirm that there is great variability of exposure between different workers and suggest the importance of performing personal exposure measurements and of detailed knowledge of the magnetic field spatial distribution.

The Procedure for Quantitative Characterization and Analysis of Magnetic Fields in Magnetic Resonance Sites for Protection of Workers: A Pilot Study

Concerning the occupational exposure in magnetic resonance imaging (MRI) facilities, the worker behavior in the magnetic resonance (MR) room is of such particular importance that there is the need for a simple but reliable method to alert the worker of the highest magnetic field exposure. Here, we describe a quantitative analysis of occupational exposure in different MRI working environments: in particular, we present a field measurement method integrated with a software tool for an accurate mapping of the fringe field in the proximity of the magnetic resonance bore. Three illustrative assessment studies are finally presented, compared and discussed, considering an example of a realistic path followed by an MRI worker during the daily procedure. The results show that the basic restrictions set by ICNIRP can be exceeded during standard procedure even in 1.5 T scanners. Using the described simplified metrics, it is possible to introduce behavioral rules on how to move around an MRI room that could be more useful than a numerical limit to aid magnetic field risk mitigation strategies.

Non-Ionizing Radiation in Swedish Health Care-Exposure and Safety Aspects

The main aim of the study was to identify and describe methods using non-ionizing radiation (NIR) such as electromagnetic fields (EMF) and optical radiation in Swedish health care. By examining anticipated exposure levels and by identifying possible health hazards we also aimed to recognize knowledge gaps in the field. NIR is mainly used in health care for diagnosis and therapy. Three applications were identified where acute effects cannot be ruled out: magnetic resonance imaging (MRI), transcranial magnetic stimulation (TMS) and electrosurgery. When using optical radiation, such as class 3 and 4 lasers for therapy or surgical procedures and ultra-violet light for therapy, acute effects such as unintentional burns, photo reactions, erythema and effects on the eyes need to be avoided. There is a need for more knowledge regarding long-term effects of MRI as well as on the combination of different NIR exposures. Based on literature and after consulting staff we conclude that the health care professionals' knowledge about the risks and safety measures should be improved and that there is a need for clear, evidence-based information from reliable sources, and it should be obvious to the user which source to address.

Human exposures to rare earth elements: Present knowledge and research prospects

The extensive use of rare earth elements (REEs) in a number of technologies is expected to impact on human health, including occupational and environmental REE exposures. A body of experimental evidence on REE-associated toxicity has been accumulated in recent decades, thus providing extensive background information on the adverse effects of REE exposures. Unlike experimental studies, the consequences of REE exposures to human health have been subjected to relatively fewer investigations. Geographical studies have been conducted on residents in REE mining districts, reporting on REE bioaccumulation, and associations between REE residential exposures and adverse health effects. A recent line of studies has associated tobacco smoking and indoor smoke with increased levels of some REEs in exposed residents. A body of literature has been focused on occupational REE exposures, with the observation of respiratory tract damage. The occupations related to REE mining and processing have shown REE bioaccumulation in scalp hair, excess REE urine levels, and defective gene expression. As for other REE occupational exposures, mention should be made of: a) jobs exposing to REE aerosol, such as movie operator; b) e-waste processing and, c) diesel engine repair and maintenance, with exposures to exhaust microparticulate (containing nanoCeO₂ as a catalytic additive). Diesel exhaust microparticulate has been studied in animal models, leading to evidence of several pathological effects in animals exposed by respiratory or systemic routes. A working hypothesis for REE occupational exposures is raised on REE-based supermagnet production and manufacture, by reviewing experimental studies that suggest several pathological effects of static magnetic fields, and warrant further investigations.

TOWARDS A PERSONALISED AND INTERACTIVE ASSESSMENT OF OCCUPATIONAL EXPOSURE TO MAGNETIC FIELD DURING DAILY ROUTINE IN MAGNETIC RESONANCE

Magnetic resonance imaging (MRI) is one of the most common sources of electromagnetic (EM) fields as a diagnostic technique widely used in medicine. MRI staff during the working day is constantly exposed to static and spatially heterogeneous magnetic field. Also, moving around the MRI room to perform their functions, workers are exposed to slowly time-varying magnetic fields that induce electrical currents and fields in the body. The development of new exposure assessment methodologies to collect exposure data at a personal level using simple everyday equipment is hence necessary, also in view of future epidemiological studies. This paper describes the design and testing of a novel device for assessing personal exposure to static and time-varying magnetic fields during daily clinical practice. The dosemeter will be also used to ensure effective training of technicians who will be instructed to avoid, where possible, risk behaviour in terms of high exposure.

Assessing Exposures to Magnetic Resonance Imaging's Complex Mixture of Magnetic Fields for In Vivo, In Vitro, and Epidemiologic Studies of Health Effects for Staff and Patients

A complex mixture of electromagnetic fields is used in magnetic resonance imaging (MRI): static, low-frequency, and radio frequency magnetic fields. Commonly, the static magnetic field ranges from one to three Tesla. The low-frequency field can reach several millitesla and with a time derivative of the order of some Tesla per second. The radiofrequency (RF) field has a magnitude in the microtesla range giving rise to specific absorption rate values of a few Watts per kilogram. Very little attention has been paid to the case where there is a combined exposure to several different fields at the same time. Some studies have shown genotoxic effects in cells after exposure to an MRI scan while others have not demonstrated any effects. A typical MRI exam includes muliple imaging sequences of varying length and intensity, to produce different types of images. Each sequence is designed with a particular purpose in mind, so one sequence can, for example, be optimized for clearly showing fat water contrast, while another is optimized for high-resolution detail. It is of the utmost importance that future experimental studies give a thorough description of the exposure they are using, and not just a statement such as “An ordinary MRI sequence was used.” Even if the sequence is specified, it can differ substantially between manufacturers on, e.g., RF pulse height, width, and duty cycle. In the latest SCENIHR opinion, it is stated that there is very little information regarding the health effects of occupational exposure to MRI fields, and long-term prospective or retrospective cohort studies on workers are recommended as a high priority. They also state that MRI is increasingly used in pediatric diagnostic imaging, and a cohort study into the effects of MRI exposure on children is recommended as a high priority. For the exposure assessment in epidemiological studies, there is a clear difference between patients and staff and further work is needed on this. Studies that explore the possible differences between MRI scan sequences and compare them in terms of exposure level are warranted.

Occupational exposure to electromagnetic fields in magnetic resonance environment: basic aspects and review of exposure assessment approaches

The purpose of this review is to make a contribution to build a comprehensive knowledge of the main aspects related to the occupational exposure to electromagnetic fields (EMFs) in magnetic resonance imaging (MRI) environments. Information has been obtained from original research papers published in international peer-reviewed journals in the English language and from documents published by governmental bodies and authorities. An overview of the occupational exposure scenarios to static magnetic fields, motion-induced, time-varying magnetic fields, and gradient and radiofrequency fields is provided, together with a summary of the relevant regulation for limiting exposure. A particular emphasis is on reviewing the main EMF exposure assessment approaches found in the literature. Exposure assessment is carried out either by measuring the unperturbed magnetic fields in the MRI rooms, or by personal monitoring campaigns, or by the use of numerical methods. A general lack of standardization of the procedures and technologies adopted for exposure assessment has emerged, which makes it difficult to perform a direct comparison of results from different studies carried out by applying different assessment strategies. In conclusion, exposure assessment approaches based on data collection and numerical models need to be better defined in order to respond to specific research questions. That would provide for a more complete characterization of the exposure patterns and for identification of the factors determining the exposure variability. Graphical abstract Main approaches adopted in the literature to perform occupational exposure assessment to electromagnetic fields (EMFs) in magnetic resonance imaging (MRI) environments. SMF: static magnetic field; GMF: gradient magnetic fields; RF: radio-frequencies.

OCCUPATIONAL EXPOSURE OF NMR SPECTROMETRISTS TO STATIC AND RADIOFREQUENCY FIELDS

Occupational exposure to static and radiofrequency fields emitted by nuclear magnetic resonance spectrometers was assessed through systematic field metering during operation of 19 devices in nine research centers. Whereas no measurable levels of radiofrequency radiation were registered outside the spectrometers, significant exposure to static field was detected, with maximum values recorded at the user's hand (B = 683.00 mT) and head-thorax (B = 135.70 mT) during spectrometer manipulation. All values were well below the exposure limits set by the European standard for workers protection against the effects of acute field exposure only. As for potential effects of chronic exposure, waiting for more complete knowledge, adoption of technical and operational strategies for exposure minimizing is advisable. In this respect, the data revealed that compared with standard magnetic shielding, ultrashield technology allows a 20-65-fold reduction of the field strength received by the operator.

MRI-related magnetic field exposures and risk of commuting accidents - A cross-sectional survey among Dutch imaging technicians

BACKGROUND

Imaging technicians working with magnetic resonance imaging (MRI) may experience acute effects such as vertigo or dizziness when being exposed. A previous study also reported an increased risk of accidents in MRI exposed staff.

OBJECTIVES

We aimed at evaluating commuting accident risk in Dutch imaging technicians.

METHODS

Of invited imaging technicians, 490 (29%) filled in a questionnaire pertaining to (near) accidents when driving or riding a bike, health, lifestyle and work practices. We used logistic regression to evaluate the association between exposure to MRI-related electromagnetic fields and risk of commuting (near) accidents in the year prior to the survey, adjusted for a range of potential confounders.

RESULTS

Our cross-sectional study indicated an increased risk of (near) accidents if imaging technicians had worked with MRI in the year prior to the survey (odds ratio OR 2.13, 95%CI 1.23-3.69). Risks were higher in persons who worked with MRI more often (OR 2.32, 95%CI 1.25-4.31) compared to persons who worked sometimes with MRI (OR 1.91, 95%CI 0.98-3.72), and higher in those who had likely experienced higher peak exposures to static and time-varying magnetic fields (OR 2.18, 95%CI 1.06-4.48). The effect was seen on commuting accidents that had occurred on the commute from home to work as well as accidents from work to home or elsewhere.

CONCLUSION

Imaging technicians working with MRI scanners may be at an increased risk of commuting (near) accidents. This result needs confirmation and potential risks for other groups (volunteers, patients) should be investigated.