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Frankel, J., Hansson Mild, K., Olsrud, J. & Wilén, J. (2019). EMF exposure variation among MRI sequences from pediatric examination protocols. Bioelectromagnetics, 40(1), 3-15
Open this publication in new window or tab >>EMF exposure variation among MRI sequences from pediatric examination protocols
2019 (English)In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 40, no 1, p. 3-15Article in journal (Refereed) Published
Abstract [en]

The magnetic resonance imaging (MRI) exposure environment is unique due to the mixture and intensity of magnetic fields involved. Current safety regulations are based on well-known acute effects of heating and neuroexcitation while the scientific grounds for possible long-term effects from MRI exposure are lacking. Epidemiological research requires careful exposure characterization, and as a first step toward improved exposure assessment we set out to characterize the MRI-patient exposure environment. Seven MRI sequences were run on a 3-Tesla scanner while the radiofrequency and gradient magnetic fields were measured inside the scanner bore. The sequences were compared in terms of 14 different exposure parameters. To study within-sequence variability, we varied sequence settings such as flip angle and slice thickness one at a time, to determine if they had any impact on exposure endpoints. There were significant differences between two or more sequences for all fourteen exposure parameters. Within-sequence differences were up to 60% of the corresponding between-sequence differences, and a 5-8 fold exposure increase was caused by variations in flip angle, slice spacing, and field of view. MRI exposure is therefore not only sequence-specific but also patient- and examination occurrence-specific, a complexity that requires careful consideration for an MRI exposure assessment in epidemiological studies to be meaningful. 

Place, publisher, year, edition, pages
Wiley-Blackwell, 2019
Keywords
children, electromagnetic field, epidemiology, exposure assessment, radiofrequency
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:umu:diva-155086 (URN)10.1002/bem.22159 (DOI)000453860500001 ()30500987 (PubMedID)
Funder
Swedish Research Council, 521-2013-2702
Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-10Bibliographically approved
Frankel, J., Wilén, J. & Hansson Mild, K. (2018). 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. Frontiers In Public Health, 6, Article ID 66.
Open this publication in new window or tab >>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
2018 (English)In: Frontiers In Public Health, ISSN 2296-2565, Vol. 6, article id 66Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
Keywords
electromagnetic field, occupational exposure, switched gradient field, diagnostic imaging, asurement
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:umu:diva-147347 (URN)10.3389/fpubh.2018.00066 (DOI)000429555100001 ()29594090 (PubMedID)
Available from: 2018-05-11 Created: 2018-05-11 Last updated: 2018-06-09Bibliographically approved
Mild, K. H., Friberg, S., Frankel, J. & Wilen, J. (2017). Exposure to the magnetic field from an induction loop pad for a hearing aid system. International Journal of Occupational Safety and Ergonomics, 23(1), 143-145
Open this publication in new window or tab >>Exposure to the magnetic field from an induction loop pad for a hearing aid system
2017 (English)In: International Journal of Occupational Safety and Ergonomics, ISSN 1080-3548, E-ISSN 2376-9130, Vol. 23, no 1, p. 143-145Article in journal (Refereed) Published
Abstract [en]

As a case study we have measured the magnetic field from an induction loop pad designed for hearing aid assistance. The magnitude of the field was high, although well below international guidelines. We recorded values up to 70% of the recommended standard in some instances. However, in view of the many reports indicating health effects of low-level exposure, we recommend that the precautionary principle is applied when such pads are given to people who might be especially vulnerable, such as children, pregnant women and women on breast cancer medication.

Keywords
hearing aid, cancer, reproduction, tamoxifen
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:umu:diva-132622 (URN)10.1080/10803548.2016.1226597 (DOI)000393712900016 ()
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2018-06-09Bibliographically approved
Bäcklund, T., Frankel, J., Israelsson, H., Malm, J. & Sundström, N. (2017). Trunk sway in idiopathic normal pressure hydrocephalus: quantitative assessment in clinical practice. Gait & Posture, 62-70, Article ID 54.
Open this publication in new window or tab >>Trunk sway in idiopathic normal pressure hydrocephalus: quantitative assessment in clinical practice
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2017 (English)In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, p. 62-70, article id 54Article in journal (Refereed) Published
Abstract [en]

Background: In diagnosis and treatment of patients with idiopathic normal pressure hydrocephalus (iNPH), there is need for clinically applicable, quantitative assessment of balance and gait. Using a body worn gyroscopic system, the aim of this study was to assess postural stability of iNPH patients in standing, walking and during sensory deprivation before and after cerebrospinal fluid (CSF) drainage and surgery. A comparison was performed between healthy elderly (HE) and patients with various types of hydrocephalus (ventriculomegaly (VM)).

Methods: Trunk sway was measured in 31 iNPH patients, 22 VM patients and 58 HE. Measurements were performed at baseline in all subjects, after CSF drainage in both patient groups and after shunt surgery in the iNPH group.

Results: Preoperatively, the iNPH patients had significantly higher trunk sway compared to HE, specifically for the standing tasks (p < 0.001). Compared to VM, iNPH patients had significantly lower sway velocity during gait in three of four cases on firm support (p < 0.05). Sway velocity improved after CSF drainage and in forward-backward direction after surgery (p < 0.01). Compared to HE both patient groups demonstrated less reliance on visual input to maintain stable posture.

Conclusions: INPH patients had reduced postural stability compared to HE, particularly during standing, and for differentiation between iNPH and VM patients sway velocity during gait is a promising parameter. A reversible reduction of visual incorporation during standing was also seen. Thus, the gyroscopic system quantitatively assessed postural deficits in iNPH, making it a potentially useful tool for aiding in future diagnoses, choices of treatment and clinical follow-up. 

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Idiopathic normal pressure hydrocephalus, Trunk sway, Balance, Gait, Gyroscope
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:umu:diva-138239 (URN)10.1016/j.gaitpost.2017.02.017 (DOI)000405044400011 ()28259041 (PubMedID)
Available from: 2017-08-16 Created: 2017-08-16 Last updated: 2018-06-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4084-6652

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