title: 3T diffusion-weighted MRI of the thyroid gland with reduced distortion: preliminary results.
abstract: OBJECTIVE
  Single-shot diffusion-weighted (DW) echo planar imaging (EPI), which is commonly used for imaging the thyroid, is characterised by severe blurring and distortion. The objectives of this work were: 1, to show that a reduced-field of view (r-FOV) DW EPI technique can improve image quality; and 2, to investigate the effect of different reconstruction strategies on the resulting apparent diffusion coefficients (ADCs).
  
  
  METHODS
  We implemented a single-shot, r-FOV DW EPI technique with a two-dimensional radiofrequency excitation pulse for DW imaging of the thyroid at 3T. Images were reconstructed using root sum of squares (SOS) and an optimal-B1 reconstruction (OBR). Phantom and in vivo experiments were performed to compare r-FOV and conventional full-FOV DW EPI with root SOS and OBR.
  
  
  RESULTS
  r-FOV with OBR substantially improved image quality at 3T. In phantoms, r-FOV gave more accurate ADCs than full-FOV. In vivo r-FOV always gave lower ADC values with respect to the full-FOV technique irrespective of the reconstruction used and whether only two or multiple b-values were used to compute the ADCs.
  
  
  CONCLUSIONS
  r-FOV DW EPI can reduce image blurring and distortion at the expense of a low signal-to-noise ratio. OBR is a promising reconstruction technique for accurate ADC measurements in lower signal-to-noise ratio regimes, although further studies are needed to characterise its performance.
  
  
  CONCLUSIONS
  DW imaging of the thyroid at 3T could potentially benefit from r-FOV acquisition strategies, such as the r-FOV DW EPI technique proposed in this paper.
authors.affiliation: Department of Radiology, University of Cambridge, Cambridge, UK. valentina.taviani@cantab.net
authors.forename: V
authors.initials: V
authors.lastname: Taviani
authors.forename: S
authors.initials: S
authors.lastname: Nagala
authors.forename: A N
authors.initials: AN
authors.lastname: Priest
authors.forename: M A
authors.initials: MA
authors.lastname: McLean
authors.forename: P
authors.initials: P
authors.lastname: Jani
authors.forename: M J
authors.initials: MJ
authors.lastname: Graves
mesh_terms: D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio; D013961:Thyroid Gland