Abstract

(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).

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC8751149/

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Abstract:

This paper presents radiofrequency (RF)-induced heating of single and multiple tattoos during magnetic resonance imaging (MRI) at 1.5 T and 3 T. Various tattoos of different shapes, positions, pigment, length, diameter, and gap between the tattoos was investigated. Finite-difference time-domain based electromagnetic and thermal simulations were performed to study the specific absorption rate (SAR) and temperature rise, respectively. The results indicated that tattoos influenced the induced electric field distribution and maximum magnitude of the SAR on the surface of the skin. A notable enhancement in the SAR were observed around the sharp edges, long strips, and circular loops of tattoos. Interestingly, the maximum local SAR and increase in tissue temperature strongly depend on the shape of the tattoo. Furthermore, the relative position and size of the tattoos affected RF-induced heating. The RF-induced heating of multiple tattoos were investigated considering the worst case scenarios. Our results confirm that RF-induced heating of multiple tattoos is quite different from that of single tattoo and does not follow a simple superposition of the results from a single tattoos. Moreover, the procedures presented in the simulation environment are used to facilitate RF-induced heating for patients with tattoos undergoing clinical MRI.

PDF https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9483925

Extract:

V. CONCLUSION
This study presents data regarding RF-induced heating around different types and positions of tattoos at different field strengths of MRI and investigated a substantial factors that may impact RF-induced heating. These factors include tattoo pigment, tattoo shape, tattoo thickness, multiple tattoos, gap between the tattoos, position of tattoos on a human phantom, and conductivity of iron oxide. The study reveals that tattoo shapes, and positions are the major factors that affect RF-induced heating during MRI. Furthermore, the size of the tattoos and the gap between multiple tattoos could lead to higher RF-induced heating at different field strengths of MRI. Moreover, tattoo thickness is associated with small variations in RF-induced heating.

The radio frequency of MRI interacts with the ferromagnetic material found in tattoos, especially iron oxide. In addition, the RF-induced heating is different for different types of tattoos due to the different scattered E-fields. Thus, it is essential to study RF-induced heating in tattooed patients or follow the current recommendations of the FDA guidelines to avoid tattoo patient from MRI examination. Future studies on RF-induced heating of tattoos during MRI should consider patient orientation, landmark position, location of tattoos on the human body, tattoo pigments, and imaging studies.

https://ieeexplore.ieee.org/document/9483925

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Abstract

Magnetic resonance imaging (MRI) has become the gold standard for the diagnosis of many pathologies. Using MRI in patients with auditory implants can however raise concerns due to mutual interactions between the implant and imaging device, resulting in potential patient risks. Several implant manufacturers have been working towards more MRI safe devices. Older devices are however often labelled for more stringent conditions, possibly creating confusion with patients and professionals. With this myriad of different devices that are implanted in patients for lifetimes of at least 20 years, it is crucial that both patients and professionals have a clear understanding of the safety of their devices. This work aims at providing an exhaustive overview on the MRI safety of active auditory implants.

The available industry standards that are followed by manufacturers are outlined and an overview of the latest scientific developments focusing on the last five years is provided. In addition, based on the analysis of the adverse events reported to the Food and Drug Administration (FDA) and in literature within the past ten years, a systematic review of the most commonly occurring issues for patients with auditory implants in the MRI environment is provided.

Results indicate that despite the release of more MRI conditional active hearing implants on the market, adverse events still occur. An extensive overview is provided on the MRI safety of active auditory implants, aiming to increase the understanding of the topic for healthcare professionals and contribute to safer scanning conditions for patients.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8241703/

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Abstract

Exposure to radiofrequency (RF) power deposition during magnetic resonance imaging (MRI) induces elevated body‐tissue temperatures and may cause changes in heart and breathing rates, disturbing thermoregulation. Eleven temperature sensors were placed in muscle tissue and one sensor in the rectum (measured in 10 cm depth) of 20 free‐breathing anesthetized pigs to verify temperature curves during RF exposure. Tissue temperatures and heart and breathing rates were measured before, during, and after RF exposure. Pigs were placed into a 60‐cm diameter whole‐body resonator of a 3 T MRI system. Nineteen anesthetized pigs were divided into four RF exposure groups: sham (0 W/kg), low‐exposure (2.7 W/kg, mean exposure time 56 min), moderate‐exposure (4.8 W/kg, mean exposure time 31 min), and high‐exposure (4.4 W/kg, mean exposure time 61 min). One pig was exposed to a whole‐body specific absorption rate (wbSAR) of 11.4 W/kg (extreme‐exposure). Hotspot temperatures, measured by sensor 2, increased by mean 5.0 ± 0.9°C, min 3.9; max 6.3 (low), 7.0 ± 2.3°C, min 4.6; max 9.9 (moderate), and 9.2 ± 4.4°C, min 6.1, max 17.9 (high) compared with 0.3 ± 0.3°C in the sham‐exposure group (min 0.1, max 0.6). Four time‐temperature curves were identified: sinusoidal, parabolic, plateau, and linear. These curve shapes did not correlate with RF intensity, rectal temperature, breathing rate, or heart rate. In all pigs, rectal temperatures increased (2.1 ± 0.9°C) during and even after RF exposure, while hotspot temperatures decreased after exposure. When rectal temperature increased by 1°C, hotspot temperature increased up to 42.8°C within 37 min (low‐exposure) or up to 43.8°C within 24 min (high‐exposure). Global wbSAR did not correlate with maximum hotspot.

Bioelectromagnetics. 2020; 1–14. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society

https://onlinelibrary.wiley.com/doi/10.1002/bem.22311

CONCLUSION

RF exposure at 4 W/kg in 20 anesthetized pigs leads to hotspot temperatures exceeding 40°C, which is above accepted IEC limits. The hotspot temperature courses show four different curve shapes (sinusoidal, parabolic, plateau, and linear), which are influenced by breathing and heart rates. Rectal temperatures are lower and delayed compared to hotspot temperatures. Possibly, patient safety may be improved by online body core measurement to guide MRI, and individually adapt SAR exposure (higher or lower) for each patient.

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Author Information Health Physics: March 2017 – Volume 112 – Issue 3 – p 305-321

doi: 10.1097/HP.0000000000000654

Abstract

Use of non-ionizing radiation (NIR) for diagnostic purposes allows non-invasive assessment of the structure and function of the human body and is widely employed in medical care. ICNIRP has published previous statements about the protection of patients during medical magnetic resonance imaging (MRI), but diagnostic methods using other forms of NIR have not been considered. This statement reviews the range of diagnostic NIR devices currently used in clinical settings; documents the relevant regulations and policies covering patients and health care workers; reviews the evidence around potential health risks to patients and health care workers exposed to diagnostic NIR; and identifies situations of high NIR exposure from diagnostic devices in which patients or health care workers might not be adequately protected by current regulations. Diagnostic technologies were classified by the types of NIR that they employ. The aim was to describe the techniques in terms of general device categories which may encompass more specific devices or techniques with similar scientific principles. Relevant legally-binding regulations for protection of patients and workers and organizations responsible for those regulations were summarized. Review of the epidemiological evidence concerning health risks associated with exposure to diagnostic NIR highlighted a lack of data on potential risks to the fetus exposed to MRI during the first trimester, and on long-term health risks in workers exposed to MRI. Most of the relevant epidemiological evidence that is currently available relates to MRI or ultrasound. Exposure limits are needed for exposures from diagnostic technologies using optical radiation within the body. There is a lack of data regarding risk of congenital malformations following exposure to ultrasound in utero in the first trimester and also about the possible health effects of interactions between ultrasound and contrast media.

https://journals.lww.com/health-physics/Fulltext/2017/03000/ICNIRP_Statement_on_Diagnostic_Devices_Using.10.aspx

PDF available at the above link

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The post Occupational exposure to electromagnetic fields from medical sources. appeared first on EMFSA.

Abstract

Over the past decades, the use of common sources of electromagnetic fields such as Wi-Fi routers and mobile phones has been increased enormously all over the world. Increased release of mercury from dental amalgam restorations after exposure to electromagnetic fields such as those generated by MRI and mobile phones has been reported by our team and other researchers. We have recently shown that some of the papers which reported no increased release of mercury after MRI, may have some methodological errors.  https://www.ncbi.nlm.nih.gov/pubmed/26544100

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