Numerically‐simulated induced electric field and current density within a human model located close to a <i>z</i>‐gradient coil

Li, Yan; Hand, J.W.; Wills, Tim; Hajnal, Joseph V.

doi:10.1002/jmri.21137

Cited by 22 publications

(9 citation statements)

References 22 publications

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“…As the basic restrictions are given in terms of induced fields or SAR, numerical simulations [82] of the field interactions using anatomically realistic models may be required to demonstrate compliance. Both quasistatic finite difference [83,84] and finite integration numerical [85] techniques have been applied. These techniques provide highly detailed anatomical distributions of induced fields and currents, but inherently involve several uncertainties.…”

Section: Modelling Of Induced Fields In Tissuementioning

confidence: 99%

Occupational exposure in MRI

McRobbie¹

2012

BJR

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This article reviews occupational exposure in clinical MRI; it specifically considers units of exposure, basic physical interactions, health effects, guideline limits, dosimetry, results of exposure surveys, calculation of induced fields and the status of the European Physical Agents Directive. Electromagnetic field exposure in MRI from the static field B(0), imaging gradients and radiofrequency transmission fields induces electric fields and currents in tissue, which are responsible for various acute sensory effects. The underlying theory and its application to the formulation of incident and induced field limits are presented. The recent International Commission on Non-Ionizing Radiation Protection (ICNIRP) Bundesministerium für Arbeit und Soziales and Institute of Electrical and Electronics Engineers limits for incident field exposure are interpreted in a manner applicable to MRI. Field measurements show that exposure from movement within the B(0) fringe field can exceed ICNIRP reference levels within 0.5 m of the bore entrance. Rate of change of field dB/dt from the imaging gradients is unlikely to exceed the new limits, although incident field limits can be exceeded for radiofrequency (RF) exposure within 0.2-0.5 m of the bore entrance. Dosimetric surveys of routine clinical practice show that staff are exposed to peak values of 42 ± 24% of B(0), with time-averaged exposures of 5.2 ± 2.8 mT for magnets in the range 0.6-4 T. Exposure to time-varying fields arising from movement within the B(0) fringe resulted in peak dB/dt of approximately 2 T s(-1). Modelling of induced electric fields from the imaging gradients shows that ICNIRP-induced field limits are unlikely to be exceeded in most situations; however, movement through the static field may still present a problem. The likely application of the limits is discussed with respect to the reformulation of the European Union (EU) directive and its possible implications for MRI.

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Section: Modelling Of Induced Fields In Tissuementioning

confidence: 99%

Occupational exposure in MRI

McRobbie¹

2012

BJR

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“…It is hard to imagine a practical implementation of “speed limits” in the context of a clinical MR scanner, particularly in an emergency situation. During the preparation of this work, important modeling studies have been published that confirm that workers moving at 1 m second –1 near a 1.5T scanner will exceed the exposure limits (18), and that standing near a gradient operating at 10 mT m –1 similarly exceeds the limit at 1 kHz (19).…”

Section: Discussionmentioning

confidence: 97%

British association of MR radiographers (BAMRR) safety survey 2005: Potential impact of European Union (EU) Physical Agents Directive (PAD) on electromagnetic fields (EMF)

Moore

Scurr

2007

Magnetic Resonance Imaging

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Purpose: To measure the potential impact on clinical MRI practice in the UK of the European Union (EU) Physical Agents Directive (PAD) on electromagnetic fields (EMF). There is evidence that the exposure limit values contained in the PAD will make it impossible for members of staff to stand close to the magnet during scanning; currently this is common practice in order to provide care and support for vulnerable patients. Interventional MR procedures will also be impossible. Materials and Methods:Members of the British Association of MR Radiographers (BAMRR) were sent a questionnaire to assess the impact of the PAD and related safety issues.Results: A total of 25% of responding sites have at least one sedation/general anesthesia (GA) session per week, while only 3% reported any interventional practice. A total of 29% of respondents reported that operators give a bolus injection by hand during contrast-enhanced magnetic resonance angiography (CE-MRA) scans. Overall it is estimated that 3% of all MR examinations in the UK are performed with a staff member in the magnet room. Some of these examinations would be impossible without staff in the room and it would be necessary for patients to have computed tomography (CT) instead of MRI. The additional radiation dose of substituting CT for MRI is estimated at 224 mansievert per year. Conclusion:While the financial costs of implementing the PAD (EMF) are relatively low, the social costs are difficult to quantify but potentially more alarming.

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“…There are multiple factors influencing the interactions of gradient fields with biological tissues and they depend on the frequency of the gradient field, the maximum and average flux densities, the presence of harmonic frequencies, the waveform characteristics of the signal, the polarity of the signal, the current distribution in the body, the electrical properties, and the sensitivity of the cell membrane [119–121,118,126,31,128,37,131,133,63,134]. The acoustic noise during an MRI exam is also caused by the gradient system [121,118].…”

Section: Peripheral Nerve Stimulation and Hearing Damage Caused By Thmentioning

confidence: 99%

Magnetic resonance safety

Sammet

2016

Abdom Radiol

141

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Magnetic Resonance Imaging (MRI) has a superior soft-tissue contrast compared to other radiological imaging modalities and its physiological and functional applications have led to a significant increase in MRI scans worldwide. A comprehensive MRI safety training to protect patients and other healthcare workers from potential bio-effects and risks of the magnetic fields in an MRI suite is therefore essential. The knowledge of the purpose of safety zones in an MRI suite as well as MRI appropriateness criteria is important for all healthcare professionals who will work in the MRI environment or refer patients for MRI scans. The purpose of this article is to give an overview of current magnetic resonance safety guidelines and discuss the safety risks of magnetic fields in an MRI suite including forces and torque of ferromagnetic objects, tissue heating, peripheral nerve stimulation and hearing damages. MRI safety and compatibility of implanted devices, MRI scans during pregnancy and the potential risks of MRI contrast agents will also be discussed and a comprehensive MRI safety training to avoid fatal accidents in an MRI suite will be presented.

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Numerically‐simulated induced electric field and current density within a human model located close to a z‐gradient coil

Cited by 22 publications

References 22 publications

Occupational exposure in MRI

Occupational exposure in MRI

British association of MR radiographers (BAMRR) safety survey 2005: Potential impact of European Union (EU) Physical Agents Directive (PAD) on electromagnetic fields (EMF)

Magnetic resonance safety

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