A Personal Dosimeter Prototype for Static Magnetic Fields

Cavagnetto, F.; Prati, P.; Ariola, V.; Corvisiero, P.; Marinelli, M.; A, Pilot; Taccini, G.

doi:10.1097/00004032-199308000-00007

Cited by 5 publications

(4 citation statements)

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“…Monitoring of staff directly requires the ability to measure static and time-varying magnetic fields. Several commercial and bespoke devices have used a combination of Hall effect sensors, induction coils and integrators [68][69][70][71][72] to measure B and dB/dt or, uniquely, to measure the induced E i field directly [73]. Any monitoring device must be lightweight, unobtrusive, non-ferromagnetic and have sufficient battery life for at least one work shift.…”

Section: Staff Dosemetersmentioning

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: Staff Dosemetersmentioning

confidence: 99%

Occupational exposure in MRI

McRobbie¹

2012

BJR

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“…The magnetic field exposure of MR personnel has also been investigated in the environment of MR systems up to 4 T [4,[11][12][13]. A report concerning magnetic field exposure of a few sample measurements in the environment of 1.0, 1.5, 3 and 7 T MR systems has been published in which volunteers' movements in the stray field were filmed with cameras, and the exposure was calculated using data from prior B field mapping [14].…”

Section: Introductionmentioning

confidence: 99%

MR safety: simultaneous B 0, dΦ/dt, and dB/dt measurements on MR-workers up to 7 T

Groebner

Umathum

Bock

et al. 2011

Magn Reson Mater Phy

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“…Until recently, personal exposure measurements were not possible and exposure was estimated from movement patterns of workers through the magnetic stray field (9) or based on simulations (10–14), because available measurement devices to measure the static magnetic field were too large and heavy to be worn during work without interfering with normal protocol. Relatively small and lightweight personal dosimeters have now been developed that can be worn for a working day without interfering with work practice (6;13–17), and thus enable assessment of personal exposure levels, and sources of variability that cause individual workers to be differently exposed even when performing tasks at similar systems. The first few exploratory quantitative exposure measurements during actual work procedures have been collected in the health care industry (6), but outside MRI rooms in hospitals, no personal exposure data are currently available.…”

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confidence: 99%

Personal exposure to static and time‐varying magnetic fields during MRI system test procedures

Vocht

Müller

Engels

et al. 2009

Magnetic Resonance Imaging

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Purpose: To assess personal time-weighted average (TWA) static magnetic field and time-varying magnetic field exposure for several system testing tasks routinely conducted by engineers at an MRI manufacturing plant. Materials and Methods:Personal exposure was measured using a personal dosimeter that measured B and dB/dt in all three orthogonal directions with a 1 Hz frequency. TWA exposure was calculated and random effects and linear mixed effects models were used to assess exposure levels and variability.Results: Whereas full-body peak (2T) and TWA (200 mT/ 8 h) exposure limits for the static magnetic field originally proposed by ICNIRP were not exceeded, time-varying magnetic field peaks (dB/dt) did exceed the proposed threshold value (767.9 mT/s) suggested by IEEE on several occasions at the 3.0 Tesla (T) whole-body cylindrical system. Conclusion:TWA exposure levels are well below the proposed limit values, but peak exposure limits are exceeded during certain procedures performed on 1.0T to 3.0T systems.

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A Personal Dosimeter Prototype for Static Magnetic Fields

Cited by 5 publications

References 0 publications

Occupational exposure in MRI

Occupational exposure in MRI

MR safety: simultaneous B 0, dΦ/dt, and dB/dt measurements on MR-workers up to 7 T

Personal exposure to static and time‐varying magnetic fields during MRI system test procedures

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