title: In vitro and in vivo comparison of wrist MR imaging at 3.0 and 7.0 tesla using a gradient echo sequence and identical eight-channel coil array designs.
abstract: OBJECTIVE
  To evaluate in vivo MR imaging of the wrist at 3.0 Tesla (T) and 7.0T quantitatively and qualitatively.
  
  
  METHODS
  To enable unbiased signal-to-noise ratio (SNR) comparisons, geometrically identical eight-channel receiver arrays were used at both field strengths. First, in vitro images of a phantom bottle were acquired at 3.0T and 7.0T to obtain an estimate of the maximum SNR gain that can be expected. MR images of the dominant wrist of 10 healthy volunteers were acquired at both field strengths. All measurements were done using the same sequence parameters. Quantitative SNR maps were calculated on a pixel-by-pixel basis and analyzed in several regions-of-interest. Furthermore, the images were qualitatively evaluated by two independent radiologists.
  
  
  RESULTS
  The quantitative analysis showed SNR increases of up to 100% at 7.0T compared with 3.0T, with considerable variation between different anatomical structures. The qualitative analysis revealed no significant difference in the visualization of anatomical structures comparing 3.0T and 7.0T MR images (P>0.05).
  
  
  CONCLUSIONS
  The presented results establish the SNR benefits of the transition from 3.0T to 7.0T for wrist imaging without bias by different array designs and based on exact, algebraic SNR quantification. The observed SNR increase nearly reaches expected values but varies greatly between different tissues. It does not necessarily improve the visibility of anatomic structures but adds valuable latitude for sequence optimization.
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Jurek A
authors.initials: JA
authors.lastname: Nordmeyer-Massner
authors.forename: Michael
authors.initials: M
authors.lastname: Wyss
authors.forename: Gustav
authors.initials: G
authors.lastname: Andreisek
authors.forename: Klaas P
authors.initials: KP
authors.lastname: Pruessmann
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
mesh_terms: D000328:Adult; D016477:Artifacts; D002358:Cartilage, Articular / Q000473:pathology; D004867:Equipment Design; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D019047:Phantoms, Imaging; D014953:Wrist / Q000473:pathology; D014955:Wrist Joint / Q000473:pathology*