title: Comparison between diffusion-weighted MRI (DW-MRI) at 1.5 and 3 tesla: a phantom study.
abstract: OBJECTIVE
  To compare DW-MRI between 1.5 and 3 Tesla (T) in terms of image quality, apparent diffusion coefficient (ADC), reproducibility, lesion-to-background contrast and signal-to-noise ratio (SNR), using a test object.
  
  
  METHODS
  A spherical diffusion phantom was used for qualitatively assessing image quality and performing quantitative measurements between the two field strengths.
  
  
  RESULTS
  Distortions and signal losses degraded image quality at 3T even when the protocols were optimized for minimum TE. The ADC, in the majority of the phantom compartments, was significantly different between 1.5T and 3T (P < 0.009), while the average coefficient of variation, excluding the phantom compartments affected by artifacts, was <1.3% at both field strengths. The lesion-to-background contrast was improved at 1.5T for images acquired with b = 1000 s/mm(2) and comparable contrast was achieved at 3T with higher b-values. The SNR gain at 3T could, in theory, be balanced by the increased number of signal excitations one can accommodate at 1.5T to perform DW-MRI within the same acquisition time and possibly improved image quality, when 3T systems with no parallel transmission are used.
  
  
  CONCLUSIONS
  Further phantom and in vivo studies are required to investigate the utility of DW-MRI at 3T, if image quality and acquisition times comparable to the ones from 1.5T are assumed.
authors.affiliation: Comprehensive Cancer Imaging Centre (C.C.I.C.), Department of Surgery and Cancer, Hammersmith Campus, Imperial College, London, United Kingdom.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Lavdas
authors.forename: Marc E
authors.initials: ME
authors.lastname: Miquel
authors.forename: Donald W
authors.initials: DW
authors.lastname: McRobbie
authors.forename: Eric O
authors.initials: EO
authors.lastname: Aboagye
mesh_terms: D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio
keywords: 3 Tesla; diffusion-weighted MRI; image quality; lesion-to-background ratio; reproducibility; signal-to-noise ratio