title: Diffusion-weighted echo planar MR imaging of the neck at 3 T using integrated shimming: comparison of MR sequence techniques for reducing artifacts caused by magnetic-field inhomogeneities.
abstract: OBJECTIVE
  Our objective was to compare available techniques reducing artifacts in echo planar imaging (EPI)-based diffusion-weighed magnetic resonance imaging MRI (DWI) of the neck at 3 Tesla caused by B0-field inhomogeneities.
  
  
  METHODS
  A cylindrical fat-water phantom was equipped with a Maxwell coil allowing for additional linear B0-field variations in z-direction. The effect of increasing strength of this superimposed gradient on image quality was observed using a standard single-shot EPI-based DWI sequence (sEPI), a zoomed single-shot EPI sequence (zEPI), a readout-segmented EPI sequence (rsEPI), and an sEPI sequence with integrated dynamic shimming (intEPI) on a 3-Tesla system. Additionally, ten volunteers were examined over the neck region using these techniques. Image quality was assessed by two radiologists. Scan durations were recorded.
  
  
  RESULTS
  With increasing strength of the external gradient, marked distortions, signal loss, and failure of fat suppression were observed using sEPI, zEPI, and rsEPI. These artifacts were markedly reduced using intEPI. Significantly better in vivo image quality was also observed using intEPI compared with the other techniques. Scan time of intEPI was similar to sEPI and zEPI and shorter than rsEPI.
  
  
  CONCLUSIONS
  The use of integrated 2D shim and frequency adjustment for EPI-based DWI results in a significant improvement in image quality of the head/neck region at 3 Tesla. Combining integrated shimming with rsEPI or zEPI can be expected to provide additional improvements.
authors: Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany. sergios.gatidis@med.uni-tuebingen.de.|Department of Radiology, University Hospital Tübingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany. sergios.gatidis@med.uni-tuebingen.de.
authors: Sergios
authors: http://orcid.org/0000-0002-6928-4967
authors: S
authors: Gatidis
authors: Siemens Healthcare GmbH, Erlangen, Germany.
authors: Hansjörg
authors: H
authors: Graf
authors: Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany.
authors: Jakob
authors: J
authors: Weiß
authors: Siemens Healthcare GmbH, Erlangen, Germany.
authors: Alto
authors: A
authors: Stemmer
authors: Siemens Healthcare GmbH, Erlangen, Germany.
authors: Berthold
authors: B
authors: Kiefer
authors: Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany.
authors: Konstantin
authors: K
authors: Nikolaou
authors: Department of Radiology, Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany.
authors: Mike
authors: M
authors: Notohamiprodjo
authors: Department of Radiology, Experimental Radiology, University of Tübingen, Tübingen, Germany.
authors: Petros
authors: P
authors: Martirosian
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry; D000328:Adult; D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D060526:Magnetic Fields; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water
keywords: Artifacts; Diffusion weighted; Echo-planar Imaging; MRI; Neck