title: Image artifacts on prostate diffusion-weighted magnetic resonance imaging: trade-offs at 1.5 Tesla and 3.0 Tesla.
abstract: OBJECTIVE
  To identify the presence and extent of artifacts in prostate diffusion-weighted magnetic resonance imaging (DW-MRI) and discuss tradeoffs between imaging at 1.5 T (1.5 T) and 3.0 T (3.0 T). In addition, we aim to provide quantitative estimates of signal-to-noise ratios (SNRs) at both field strengths.
  
  
  METHODS
  The institutional review board waived informed consent for this Health Insurance Portability and Accountability Act-compliant, retrospective study of 53 consecutive men who underwent 3.0 T endorectal DW-MRI and 53 consecutive men who underwent 1.5 T endorectal DW-MRI between October and December 2010. One radiologist and one physicist, blinded to patient characteristics, image acquisition parameters, and field strength, scored DW-MRI artifacts. On b = 0 images, SNR was measured as the ratio of the mean signal from a region of interest (ROI) at the level of the verumontanum (the "reference region") to the standard deviation from the mean signal in an artifact-free ROI in the rectum.
  
  
  RESULTS
  Both readers found geometric distortion and signal graininess significantly more often at 3.0 T than at 1.5 T (P < .0001, all comparisons). Reader 2 (but not reader 1) found ghosting artifacts more often at 3.0 T (P = .001) and blurring more often at 1.5 T (P = .006). Mean SNR at the urethra (87.92 ± 27.76) at 3.0 T was 1.43 times higher than at 1.5 T (64.51 ± 14.96) (P < .0001).
  
  
  CONCLUSIONS
  At 3.0 T (as compared to 1.5 T), increased SNR on prostate DW-MRI comes at the expense of geometric distortion and can also lead to more pronounced ghosting artifacts. Therefore, to take full advantage of the benefits of 3.0 T, further improvements in acquisition techniques are needed to address DW-MRI artifacts corresponding to higher field strengths.
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY, USA. mazahery@mskcc.org
authors.forename: Yousef
authors.initials: Y
authors.lastname: Mazaheri
authors.forename: H Alberto
authors.initials: HA
authors.lastname: Vargas
authors.forename: Gregory
authors.initials: G
authors.lastname: Nyman
authors.forename: Oguz
authors.initials: O
authors.lastname: Akin
authors.forename: Hedvig
authors.initials: H
authors.lastname: Hricak
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Diffusion-weighted imaging; MRI; artifacts; prostate cancer