Experimental determination of human peripheral nerve stimulation thresholds in a 3‐axis planar gradient system

Feldman, Rebecca E.; Hardy, Christopher J.; Aksel, Bulent; Schenck, John F.; Chronik, Blaine A.

doi:10.1002/mrm.22050

Cited by 19 publications

(22 citation statements)

References 22 publications

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“…The achievable slew rates for the coils are ∼10 times higher than typical whole‐body coils. Previous work done by Feldman et al (14) has shown that planar coils are able to operate at significantly higher slew rates than conventional cylindrical systems without causing PNS, demonstrating that the relationship between PNS and slew rate is complicated and geometry dependent. This observation was the motivation for this study.…”

Section: Discussionmentioning

confidence: 96%

“…The size constraint imposed by the scanner bore, along with the necessity of maintaining access for the subject has required that the design of these coils stray from traditional cylindrical geometry (6, 9–13). Because of their open geometry and PNS advantages (14), planar gradient insert coils have been used as additional insert coils exclusively for high‐performance diffusion‐weighted imaging (1). Challenges in planar gradient coil design include relatively poor gradient homogeneity, torque issues, asymmetric eddy‐current profiles, and a drastic decrease in efficiency as the region of interest (ROI) moves away from the coil surface.…”

Section: Introductionmentioning

confidence: 99%

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Design study to investigate the effect of curvature on gradient coil performance for localized regions of interest

Harris¹,

Handler²,

Chronik³

2012

Concepts Magn Reson

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In this study, a boundary element method has been implemented to design and analyze the performance of curved gradient coil geometries as a function of the degree of curvature over all three axes, with designs varying continuously from planar to full cylindrical. It was found that there is a monotonic increase in gradient performance with degree of curvature with little gain beyond half‐cylindrical coil geometries for a specific region of interest located 10 cm above the coil surface. The efficiencies of the half‐cylindrical geometry coils are 0.76 mT m−1 A−1, 0.71 mT m−1 A−1, and 0.76 mT m−1 A−1 for the x‐, y‐, and z‐gradient axes, respectively, when scaled to 800 μH inductance. The gradient coils presented in this study would serve as anatomically specific gradient channels to be used in conjunction with larger, whole‐body coils to comprise a 6‐channel hybrid system. The function of these channels could include the ability to provide very high performance diffusion tensor imaging in a specified volume of tissue such as the breast, prostate, or posterior regions of the brain. © 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 41B: 62–71, 2012

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Design study to investigate the effect of curvature on gradient coil performance for localized regions of interest

Harris¹,

Handler²,

Chronik³

2012

Concepts Magn Reson

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“…The fast switching gradient fields are applied for spatial encoding of the MRI signal and can cause peripheral nerve stimulation and implant heating. They are also responsible for the noise in the MRI scanner room, which can reach levels of 100 dB or more and potentially lead to hearing damages [74,119–121,118,122–126,30,31,127,128,16,90,129,37,130–133,57,58,134,135,69]. …”

Section: Magnetic Fields In An Mri Suitementioning

confidence: 99%

“…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

137

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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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“…Pulse sequences with high slew rates run the risk of inducing peripheral nerve stimulation (9). Some localized and noncylindrical gradients have been shown to have higher stimulation thresholds (10, 11) and permit rapidly switched gradient fields to be operated with larger gradient magnitudes. The obvious challenge is that restricting the field of view results in artifacts (12).…”

mentioning

confidence: 99%

Results for diffusion‐weighted imaging with a fourth‐channel gradient insert

Feldman

Scholl

Alford

et al. 2011

Magnetic Resonance in Med

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Diffusion‐weighted imaging suffers from motion artifacts and relatively low signal quality due to the long echo times required to permit the diffusion encoding. We investigated the inclusion of a noncylindrical fourth gradient coil, dedicated entirely to diffusion encoding, into the imaging system. Standard three‐axis whole body gradients were used during image acquisition, but we designed and constructed an insert coil to perform diffusion encodings. We imaged three phantoms on a 3‐T system with a range of diffusion coefficients. Using the insert gradient, we were able to encode b values of greater than 1300 s/mm2 with an echo time of just 83 ms. Images obtained using the insert gradient had higher signal to noise ratios than those obtained using the whole body gradient: at 500 s/mm2 there was a 18% improvement in signal to noise ratio, at 1000 s/mm2 there was a 39% improvement in signal to noise ratio, and at 1350 s/mm2 there was a 56% improvement in signal to noise ratio. Using the insert gradient, we were capable of doing diffusion encoding at high b values by using relatively short echo times. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.

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Experimental determination of human peripheral nerve stimulation thresholds in a 3‐axis planar gradient system

Cited by 19 publications

References 22 publications

Design study to investigate the effect of curvature on gradient coil performance for localized regions of interest

Design study to investigate the effect of curvature on gradient coil performance for localized regions of interest

Magnetic resonance safety

Results for diffusion‐weighted imaging with a fourth‐channel gradient insert

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