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  • 1. Baste, Valborg
    et al.
    Hansson Mild, Kjell
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Moen, Bente E
    Radiofrequency exposure on fast patrol boats in the Royal Norwegian Navy-an approach to a dose assessment.2010In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 31, no 5, p. 350-360Article in journal (Refereed)
    Abstract [en]

    Epidemiological studies related to radiofrequency (RF) electromagnetic fields (EMF) have mainly used crude proxies for exposure, such as job titles, distance to, or use of different equipment emitting RF EMF. The Royal Norwegian Navy (RNoN) has measured RF field emitted from high-frequency antennas and radars on several spots where the crew would most likely be located aboard fast patrol boats (FPB). These boats are small, with short distance between the crew and the equipment emitting RF field. We have described the measured RF exposure aboard FPB and suggested different methods for calculations of total exposure and annual dose. Linear and spatial average in addition to percentage of ICNIRP and squared deviation of ICNIRP has been used. The methods will form the basis of a job exposure matrix where relative differences in exposure between groups of crew members can be used in further epidemiological studies of reproductive health. Bioelectromagnetics, 2010. (c) 2010 Wiley-Liss, Inc.

  • 2. Figueroa Karlström, Eduardo
    et al.
    Lundström, Ronnie
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational Medicine.
    Stensson, Olle
    Hansson Mild, Kjell
    Therapeutic staff exposure to magnetic field pulses during TMS/rTMS treatments2006In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 27, no 2, p. 156-158Article in journal (Refereed)
    Abstract [en]

    Transcranial magnetic stimulation or repetitive transcranial magnetic stimulation (TMS/rTMS) is currently being used in treatments of the central nervous system diseases, for instance, depressive states. The principles of localized magnetic stimulation are summarized and the risk and level of occupational field exposure of the therapeutic staff is analyzed with reference to lCNIRP guidelines for pulses below 100 kHz. Measurements and analysis of the occupational exposure to magnetic fields of the staff working with TMS/rTMS are presented.

  • 3.
    Frankel, Jennifer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hansson Mild, Kjell
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Olsrud, Johan
    Wilén, Jonna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    EMF exposure variation among MRI sequences from pediatric examination protocols2019In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 40, no 1, p. 3-15Article in journal (Refereed)
    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. 

  • 4. Hansson, Boel
    et al.
    Höglund, Peter
    Markenroth Bloch, Karin
    Nilsson, Markus
    Olsrud, Johan
    Wilén, Jonna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Björkman-Burtscher, Isabella M.
    Short-term effects experienced during examinations in an actively shielded 7 T MR2019In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 40, no 4, p. 234-249Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to evaluate occurrence and strength of short‐term effects experienced by study participants in an actively shielded (AS) 7 tesla (7 T) magnetic resonance (MR) scanner, to compare results with earlier reports on passively shielded (PS) 7 T MR scanners, and to outline possible healthcare strategies to improve patient compliance. Study participants (n = 124) completed a web‐based questionnaire directly after being examined in an AS 7 T MR (n = 154 examinations). Most frequently experienced short‐term effects were dizziness (84%) and inconsistent movement (70%), especially while moving into or out of the magnet. Peripheral nerve stimulation (PNS)—twitching—was experienced in 67% of research examinations and showed a dependence between strength of twitches and recorded predicted PNS values. Of the participants, 74% experienced noise levels as acceptable and the majority experienced body and room temperature as comfortable. Of the study participants, 95% felt well‐informed and felt they had had good contact with the staff before the examination. Willingness to undergo a future 7 T examination was high (>90%). Our study concludes short‐term effects are often experienced during examinations in an AS 7 T MR, leaving room for improvement in nursing care strategies to increase patient compliance.

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  • 5.
    Hansson Mild, Kjell
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hand, Jeff
    Hietanen, Maila
    Gowland, Penny
    Karpowicz, Jolanta
    Keevil, Stephen
    Lagroye, Isabelle
    van Rongen, Eric
    Scarfi, Maria Rosaria
    Wilén, Jonna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Exposure classification of MRI workers in epidemiological studies2013In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 34, no 1, p. 81-84Article in journal (Refereed)
    Abstract [en]

    We estimate that there are about 100,000 workers from different disciplines, such as radiographers, nurses, anesthetists, technicians, engineers, etc., who can be exposed to substantial electromagnetic fields (compared to normal background levels) around magnetic resonance imaging (MRI) scanners. There is a need for well-designed epidemiological studies of MRI workers but since the exposure from MRI equipment is a very complex mixture of static magnetic fields, switched gradient magnetic fields, and radiofrequency electromagnetic fields (RF EMF), it is necessary to discuss how to assess the exposure in epidemiological studies. As an alternative to the use of job title as a proxy of exposure, we propose an exposure categorization for the different professions working with MRI equipment. Specifically, we propose defining exposure in three categories, depending on whether people are exposed to only the static field, to the static plus switched gradient fields or to the static plus switched gradient plus RF fields, as a basis for exposure assessment in epidemiological studies.

  • 6. Lyskov, Eugene
    et al.
    Kalezic, Nebojsa
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences.
    Markov, Marko
    Hanson-Mild, Kjell
    Thunberg, Johan
    Johansson, Håkan
    Low frequency therapeutic EMF differently influences experimental muscle pain in female and male subjects2005In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 26, no 4, p. 299-304Article in journal (Refereed)
  • 7.
    Sundström, Henrik
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Hansson Mild, Kjell
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wilen, Jonna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Measurements of the Ripple Effect and Geometric Distribution of Switched Gradient Fields Inside a Magnetic Resonance Scanner2015In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 36, no 2, p. 162-168Article in journal (Refereed)
    Abstract [en]

    Knowledge of patient exposure during magnetic resonance imaging (MRI) procedures is limited, and the need for such knowledge has been demonstrated in recent in vitro and in vivo studies of the genotoxic effects of MRI. This study focuses on the dB/dt of the switched gradient field (SGF) and its geometric distribution. These values were characterized by measuring the peak dB/dt generated by a programmed gradient current of alternating triangles inside a 1.5T MR scanner. The maximum dB/dt exposure to the gradient field was 6-14T/s, and this occurred at the edges of the field of view (FOV) 20-25cm from the isocenter in the longitudinal direction. The dB/dt exposure dropped off to roughly half the maximum (3-7T/s) at the edge of the bore. It was found that the dB/dt of the SGF was distorted by a 200kHz ripple arising from the amplifier. The ripple is small in terms of B-field, but the high frequency content contributes to a peak dB/dt up to 18 times larger than that predicted by the slew rate (4T/sm) and the distance from the isocenter. Measurements on a 3T MRI scanner, however, revealed a much smaller filtered ripple of 100kHz in dB/dt. These findings suggest that the gradient current to each coil together with information on the geometrical distribution of the gradient field and ripple effects could be used to assess the SGF exposure within an MRI bore.

  • 8.
    Wilén, Jonna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Exposure assessment of electromagnetic fields near electrosurgical units.2010In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 31, no 7, p. 513-518Article in journal (Refereed)
    Abstract [en]

    Electrosurgical units (ESU) are widely used in medical health services. By applying sinusoidal or pulsed voltage in the frequency range of 0.3-5 MHz to the electrode tip, the desired mixture of coagulation and cutting are achieved. Due to the high voltage and current in the cable, strong electromagnetic fields appear near the ESU. The surgeon and others inside the operating room such as nurses, anesthesiologists, etc., will be highly exposed to these fields. The stray fields surrounding the ESU have previously been measured, but now a deeper analysis has been made of the curve shape of the field and the implication of this when assessing exposure from a commonly used ESU in accordance with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. The result showed that for some of the modes, especially those using high-pulsed voltage with only a few sinusoidal periods, the E-field close to the cable could reach linear spatially averaged values of 20 kV/m compared to the 2.1 kV/m stated in ICNIRP guidelines. Assessing the E- and B-field from ESU is not straightforward since in this frequency range, both induced current density and specific absorption rate are restricted by the ICNIRP guidelines. Nevertheless, work needs to be done to reduce the stray fields from ESU. Bioelectromagnetics (c) 2010 Wiley-Liss, Inc.

  • 9.
    Wilén, Jonna
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hauksson, Jón
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hansson Mild, Kjell
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Modification of pulse sequences reduces occupational exposure from MRI switched gradient fields: Preliminary results.2010In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 31, no 1, p. 85-87Article in journal (Refereed)
    Abstract [en]

    The gradient fields in magnetic resonance imaging (MRI) will in some circumstances exceed the ICNIRP guidelines of occupational electromagnetic field exposure when personnel are near the scanner during MRI scanning. In this work we have shown that using commercially available modified sequences for noise reduction purposes, exposure will decrease by a factor of 1.5 with preserved image quality. This is a first step toward optimizing occupational exposure within the scanner room without affecting image quality. Bioelectromagnetics 31:85-87, 2010. (c) 2009 Wiley-Liss, Inc.

  • 10.
    Wilén, Jonna
    et al.
    National Institute for Working Life, Umeå, Sweden.
    Hörnsten, Rolf
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology. National Institute for Working Life, Umeå, Sweden.
    Sandström, Monica
    National Institute for Working Life, Umeå, Sweden.
    Bjerle, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology. Biomedical Engineering & Informatics, University Hospital, Umeå, Sweden.
    Stensson, Olov
    National Institute for Working Life, Umeå, Sweden.
    Lyskov, Eugene
    Centre for Musculoskeletal Research, University of Gävle, Sweden.
    Hansson Mild, Kjell
    National Institute for Working Life, Umeå, Sweden.
    Electromagnetic field exposure and health among RF plastic sealer operators2004In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 25, no 1, p. 5-15Article in journal (Refereed)
    Abstract [en]

    Operators of RF plastic sealers (RF operators) are an occupational category highly exposed to radiofrequency electromagnetic fields. The aim of the present study was to make an appropriate exposure assessment of RF welding and examine the health status of the operators. In total, 35 RF operators and 37 controls were included. The leakage fields (electric and magnetic field strength) were measured, as well as induced and contact current. Information about welding time and productivity was used to calculate time integrated exposure. A neurophysiological examination and 24 h ECG were also carried out. The participants also had to answer a questionnaire about subjective symptoms. The measurements showed that RF operators were exposed to rather intense electric and magnetic fields. The mean values of the calculated 6 min, spatially averaged E and H field strengths, in line with ICNIRP reference levels, are 107 V/m and 0.24 A/m, respectively. The maximum measured field strengths were 2 kV/m and 1.5 A/m, respectively. The induced current in ankles and wrists varied, depending on the work situation, with a mean value of 101 mA and a maximum measured value of 1 A. In total, 11 out of 46 measured RF plastic sealers exceeded the ICNIRP reference levels. RF operators, especially the ready made clothing workers had a slightly disturbed two-point discrimination ability compared to a control group. A nonsignificant difference between RF operators and controls was found in the prevalence of subjective symptoms, but the time integrated exposure parameters seem to be of importance to the prevalence of some subjective symptoms: fatigue, headaches, and warmth sensations in the hands. Further, RF operators had a significantly lower heart rate (24 h registration) and more episodes of bradycardia compared to controls.

  • 11.
    Wilén, Jonna
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Olsrud, Johan
    Frankel, Jennifer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hansson Mild, Kjell
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Valid Exposure Protocols Needed in Magnetic Resonance Imaging Genotoxic Research2020In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 41, no 3, p. 247-257Article in journal (Refereed)
    Abstract [en]

    Several in vitro and in vivo studies have investigated if a magnetic resonance imaging (MRI) examination can cause DNA damage in human blood cells. However, the electromagnetic field (EMF) exposure that the cells received in the MR scanner was not sufficiently described. The first studies looking into this could be regarded as hypothesis-generating studies. However, for further exploration into the role of MRI exposure on DNA integrity, the exposure itself cannot be ignored. The lack of sufficient method descriptions makes the early experiments difficult, if not impossible, to repeat. The golden rule in all experimental work is that a study should be repeatable by someone with the right knowledge and equipment, and this is simply not the case with many of the recent studies on MRI and genotoxicity. Here we discuss what is lacking in previous studies, and how we think the next generation of in vitro and in vivo studies on MRI and genotoxicity should be performed. Bioelectromagnetics.

  • 12.
    Wilén, Jonna
    et al.
    National Institute for Working Life.
    Sandström, Monica
    National Institute for Working Life.
    Hansson Mild, Kjell
    National Institute for Working Life.
    Subjective symptoms among mobile phone users: a consequence of absorption of radiofrequency fields?2003In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 24, no 3, p. 152-159Article in journal (Refereed)
    Abstract [en]

    In a previous epidemiological study, where we studied the prevalence of subjective symptoms among mobile phone (MP) users, we found as an interesting side finding that the prevalence of many of the subjective symptoms increased with increasing calling time and number of calls per day. In this extrapolative study, we have selected 2402 people from the epidemiological study who used any of the four most common GSM MP. We used the information about the prevalence of symptoms, calling time per day, and number of calls per day and combined it with measurements of the Specific Absorption Rate (SAR). We defined three volumes in the head and measured the maximum SAR averaged over a cube of 1 g tissue (SAR(1g)) in each volume. Two new exposure parameters Specific Absorption per Day (SAD) and Specific Absorption per Call (SAC) have been devised and are obtained as combinations of SAR, calling time per day, and number of calls per day, respectively. The results indicates that SAR values >0.5 W/kg may be an important factor for the prevalence of some of the symptoms, especially in combination with long calling times per day.

  • 13.
    Wilén, Jonna
    et al.
    National Institute for Working Life, Umeå.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Radiation Sciences.
    Hörnsten, Rolf
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Clinical Physiology.
    Sandström, Monica
    Umeå University, Faculty of Medicine, Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Changes in heart rate variability among RF plastic sealer operators.2007In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 28, no 1, p. 76-79Article in journal (Refereed)
    Abstract [en]

    In a previous study, we showed that operators of radiofrequency (RF) plastic sealers, RF operators (n = 35) had a lower heart rate during nighttime compared to a control group (n = 37). We have analyzed the heart rate variability (HRV) on the same group of people to better understand the possible underlying rhythm disturbances. We found a significantly increased total HRV and very low frequency (VLF) power during nighttime among the RF operators compared to a control group. Together with our previous finding of a significantly lower heart rate during nighttime among the RF operators compared to the controls, this finding indicates a relative increase in parasympathetic cardiac modulation in RF operators. This could in turn be due to an adaptation of the thermoregulatory system and the cardiac autonomic modulation to a long-term low-level thermal exposure in the RF operators.

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