title: High slew-rate head-only gradient for improving distortion in echo planar imaging: Preliminary experience.
abstract: To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in vivo human brain imaging, with a dedicated, head-only gradient coil.
  
  
  
  Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T magnetic resonance imaging (MRI) system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI.
  
  
  
  As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects.
  
  
  
  Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. J. Magn. Reson. Imaging 2016;44:653-664.
authors.affiliation: GE Global Research, Niskayuna, New York, USA.
authors.forename: Ek T
authors.initials: ET
authors.lastname: Tan
authors.affiliation: CNIR, IBS and Department of Biomedical Engineering Sungkyunkwan University, Suwon, South Korea.
authors.forename: Seung-Kyun
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Weavers
authors.affiliation: GE Global Research, Niskayuna, New York, USA.
authors.forename: Dominic
authors.initials: D
authors.lastname: Graziani
authors.affiliation: GE Global Research, Niskayuna, New York, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Piel
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Yunhong
authors.initials: Y
authors.lastname: Shu
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: John
authors.initials: J
authors.lastname: Huston
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Matt A
authors.initials: MA
authors.lastname: Bernstein
authors.affiliation: GE Global Research, Niskayuna, New York, USA.
authors.forename: Thomas K F
authors.initials: TK
authors.lastname: Foo
mesh_terms: D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D017352:Echo-Planar Imaging / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D010865:Pilot Projects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers
keywords: EPI; echo planar imaging; head-only gradient coil; image distortion; slew rate