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Peripheral nerve stimulation limits of a high amplitude and slew rate magnetic field gradient coil for neuroimaging.

Authors
  • Tan, Ek T1
  • Hua, Yihe1
  • Fiveland, Eric W1
  • Vermilyea, Mark E1
  • Piel, Joseph E1
  • Park, Keith J1
  • Ho, Vincent B2, 3
  • Foo, Thomas K F1
  • 1 GE Research, Niskayuna, New York.
  • 2 Uniformed Services University of the Health Sciences, Bethesda, Maryland.
  • 3 Walter Reed National Military Medical Center, Bethesda, Maryland.
Type
Published Article
Journal
Magnetic Resonance in Medicine
Publisher
Wiley (John Wiley & Sons)
Publication Date
Jan 01, 2020
Volume
83
Issue
1
Pages
352–366
Identifiers
DOI: 10.1002/mrm.27909
PMID: 31385628
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

To establish peripheral nerve stimulation (PNS) thresholds for an ultra-high performance magnetic field gradient subsystem (simultaneous 200-mT/m gradient amplitude and 500-T/m/s gradient slew rate; 1 MVA per axis [MAGNUS]) designed for neuroimaging with asymmetric transverse gradients and 42-cm inner diameter, and to determine PNS threshold dependencies on gender, age, patient positioning within the gradient subsystem, and anatomical landmarks. The MAGNUS head gradient was installed in a whole-body 3T scanner with a custom 16-rung bird-cage transmit/receive RF coil compatible with phased-array receiver brain coils. Twenty adult subjects (10 male, mean ± SD age = 40.4 ± 11.1 years) underwent the imaging and PNS study. The tests were repeated by displacing subject positions by 2-4 cm in the superior-inferior and anterior-posterior directions. The x-axis (left-right) yielded mostly facial stimulation, with mean ΔGmin = 111 ± 6 mT/m, chronaxie = 766 ± 76 µsec. The z-axis (superior-inferior) yielded mostly chest/shoulder stimulation (123 ± 7 mT/m, 620 ± 62 µsec). Y-axis (anterior-posterior) stimulation was negligible. X-axis and z-axis thresholds tended to increase with age, and there was negligible dependency with gender. Translation in the inferior and posterior directions tended to increase the x-axis and z-axis thresholds, respectively. Electric field simulations showed good agreement with the PNS results. Imaging at MAGNUS gradient performance with increased PNS threshold provided a 35% reduction in noise-to-diffusion contrast as compared with whole-body performance (80 mT/m gradient amplitude, 200 T/m/sec gradient slew rate). The PNS threshold of MAGNUS is significantly higher than that for whole-body gradients, which allows for diffusion gradients with short rise times (under 1 msec), important for interrogating brain microstructure length scales. © 2019 International Society for Magnetic Resonance in Medicine.

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